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Add value coercion examples (#913)
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‎examples/src/main/java/org/neo4j/docs/driver/ReadingValuesExample.java

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/*
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* Copyright (c) "Neo4j"
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* Neo4j Sweden AB [http://neo4j.com]
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*
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* This file is part of Neo4j.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.neo4j.docs.driver;
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import java.util.function.Function;
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import org.neo4j.driver.Record;
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import org.neo4j.driver.Result;
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import org.neo4j.driver.Session;
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import org.neo4j.driver.Value;
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import static org.neo4j.driver.Values.parameters;
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public class ReadingValuesExample extends BaseApplication
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{
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private static final String nullFieldName = "fieldName";
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private static final String intFieldName = "fieldName";
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public ReadingValuesExample( String uri, String user, String password )
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{
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super( uri, user, password );
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}
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public Boolean nullIsNull()
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{
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return echo( null, record ->
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{
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// tag::java-driver-reading-values-null[]
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Value possibleNullValue = record.get( nullFieldName );
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// Checking if its null
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boolean wasNull = possibleNullValue.isNull(); // true
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// end::java-driver-reading-values-null[]
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return wasNull;
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} );
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}
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public String nullAsString()
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{
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return echo( null, record ->
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{
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Value possibleNullValue = record.get( nullFieldName );
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// tag::java-driver-reading-values-null[]
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// Getting the null value as string
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String stringWithNullContent = possibleNullValue.asString(); // "null"
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// end::java-driver-reading-values-null[]
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return stringWithNullContent;
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} );
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}
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public Object nullAsObject()
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{
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return echo( null, record ->
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{
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Value possibleNullValue = record.get( nullFieldName );
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// tag::java-driver-reading-values-null[]
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// Getting `null` as object
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Object nullObject = possibleNullValue.asObject(); // null
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// end::java-driver-reading-values-null[]
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return nullObject;
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} );
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}
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public float nullAsObjectFloatDefaultValue()
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{
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return echo( null, record ->
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{
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Value possibleNullValue = record.get( nullFieldName );
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// tag::java-driver-reading-values-null[]
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// Coercing value with a default value set
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float floatValue = possibleNullValue.asFloat( 1.0f ); // 1.0f
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// end::java-driver-reading-values-null[]
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return floatValue;
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} );
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}
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public void nullAsObjectFloat()
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{
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echo( null, record ->
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{
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Value possibleNullValue = record.get( nullFieldName );
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// tag::java-driver-reading-values-null[]
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// Could not cast null to float
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float floatValue = possibleNullValue.asFloat(); // throws org.neo4j.driver.exceptions.value.Uncoercible
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// end::java-driver-reading-values-null[]
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return floatValue;
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} );
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}
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public Boolean integerFieldIsNull()
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{
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return echo( 4, record ->
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{
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// tag::java-driver-reading-values-non-null[]
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Value value = record.get( intFieldName );
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// Checking if the value is null
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Boolean falseBoolean = value.isNull(); // false
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// end::java-driver-reading-values-non-null[]
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return falseBoolean;
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} );
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}
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public int integerAsInteger()
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{
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return echo( 4, record ->
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{
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Value value = record.get( intFieldName );
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// tag::java-driver-reading-values-non-null[]
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// Getting as int
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int intValue = value.asInt(); // the int
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// end::java-driver-reading-values-non-null[]
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return intValue;
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} );
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}
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public long integerAsLong()
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{
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return echo( 4, record ->
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{
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Value value = record.get( intFieldName );
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// tag::java-driver-reading-values-non-null[]
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// Getting value asLong is also possible for int values
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long longValue = value.asLong(); // the int casted to long
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// end::java-driver-reading-values-non-null[]
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return longValue;
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} );
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}
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public void integerAsString()
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{
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echo( 4, record ->
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{
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Value value = record.get( intFieldName );
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// tag::java-driver-reading-values-non-null[]
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// But it's not possible to get the int value as string
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String stringValue = value.asString(); // throws org.neo4j.driver.exceptions.value.Uncoercible
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// end::java-driver-reading-values-non-null[]
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return stringValue;
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} );
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}
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private <T, O> O echo( T value, Function<Record,O> transformation )
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{
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try ( Session session = driver.session() )
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{
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return session.readTransaction( tx ->
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{
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Result result = tx.run( "RETURN $in AS fieldName", parameters( "in", value ) );
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Record record = result.next();
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return transformation.apply( record );
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} );
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}
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}
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}

‎examples/src/test/java/org/neo4j/docs/driver/ExamplesIT.java

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import org.neo4j.driver.SessionConfig;
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import org.neo4j.driver.Value;
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import org.neo4j.driver.Values;
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import org.neo4j.driver.exceptions.value.Uncoercible;
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import org.neo4j.driver.internal.util.EnabledOnNeo4jWith;
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import org.neo4j.driver.summary.QueryType;
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import org.neo4j.driver.summary.ResultSummary;
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import static org.hamcrest.Matchers.greaterThanOrEqualTo;
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import static org.hamcrest.Matchers.instanceOf;
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import static org.hamcrest.Matchers.is;
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import static org.hamcrest.Matchers.nullValue;
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import static org.hamcrest.junit.MatcherAssert.assertThat;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertThrows;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import static org.neo4j.driver.Config.TrustStrategy.trustAllCertificates;
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import static org.neo4j.driver.Values.parameters;
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assertThat( greetingCount, is( 1 ) );
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}
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}
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@Test
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void testReadingValuesExample() throws Exception
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{
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try (ReadingValuesExample example = new ReadingValuesExample( uri, USER, PASSWORD ))
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{
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assertThat( example.integerFieldIsNull(), is(false) );
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assertThat( example.integerAsInteger(), is( 4 ) );
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assertThat( example.integerAsLong(), is( 4L ) );
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assertThrows( Uncoercible.class, example::integerAsString );
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assertThat( example.nullIsNull(), is(true) );
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assertThat( example.nullAsString(), is( "null" ) );
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assertThat( example.nullAsObject(), nullValue());
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assertThat( example.nullAsObjectFloatDefaultValue(), is( 1.0f ) );
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assertThrows( Uncoercible.class, example::nullAsObjectFloat );
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}
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}
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}

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