No need to give schema to prediction engine

Author: Pete Luferenko

test/Microsoft.ML.Tests/Scenarios/Api/SimpleTrainAndPredict.cs

@@ -78,7 +78,7 @@ public void New_SimpleTrainAndPredict()
                 var model = pipeline.Fit(new MultiFileSource(dataPath));
 
                 // Create prediction engine and test predictions.
-                var engine = new MyPredictionEngine<SentimentData, SentimentPrediction>(env, model.Reader.GetOutputSchema(), model.Transformer);
+                var engine = new MyPredictionEngine<SentimentData, SentimentPrediction>(env, model.Transformer);
 
                 // Take a couple examples out of the test data and run predictions on top.
                 var testData = model.Reader.Read(new MultiFileSource(GetDataPath(SentimentTestPath)))

test/Microsoft.ML.Tests/Scenarios/Api/TrainSaveModelAndPredict.cs

@@ -101,7 +101,7 @@ public void New_TrainSaveModelAndPredict()
                 }
 
                 // Create prediction engine and test predictions.
-                var engine = new MyPredictionEngine<SentimentData, SentimentPrediction>(env, model.Reader.GetOutputSchema(), model.Transformer);
+                var engine = new MyPredictionEngine<SentimentData, SentimentPrediction>(env, model.Transformer);
 
                 // Take a couple examples out of the test data and run predictions on top.
                 var testData = model.Reader.Read(new MultiFileSource(GetDataPath(SentimentTestPath)))

test/Microsoft.ML.Tests/Scenarios/Api/TrainWithInitialPredictor.cs

@@ -69,7 +69,7 @@ public void New_TrainWithInitialPredictor()
 
                 // Train the second predictor on the same data.
                 var secondTrainer = new MyAveragedPerceptron(env, new AveragedPerceptronTrainer.Arguments(), "Features", "Label");
-                var finalPredictor = secondTrainer.Train(trainData, firstPredictor);
+                var finalPredictor = secondTrainer.Train(trainData, firstPredictor.Model);
             }
         }
 

test/Microsoft.ML.Tests/Scenarios/Api/Wrappers.cs

@@ -313,9 +313,9 @@ public MyAveragedPerceptron(IHostEnvironment env, AveragedPerceptronTrainer.Argu
 
         protected override IPredictor TrainCore(TrainContext trainContext) => _trainer.Train(trainContext);
 
-        public ITransformer Train(IDataView trainData, IPredictorTransformer<IPredictor> initialPredictor)
+        public ITransformer Train(IDataView trainData, IPredictor initialPredictor)
         {
-            return TrainTransformer(trainData, initPredictor: initialPredictor.TrainedModel);
+            return TrainTransformer(trainData, initPredictor: initialPredictor);
         }
     }
 
@@ -325,9 +325,9 @@ public sealed class MyPredictionEngine<TSrc, TDst>
     {
         private readonly PredictionEngine<TSrc, TDst> _engine;
 
-        public MyPredictionEngine(IHostEnvironment env, ISchema inputSchema, ITransformer pipe)
+        public MyPredictionEngine(IHostEnvironment env, ITransformer pipe)
         {
-            IDataView dv = new EmptyDataView(env, inputSchema);
+            IDataView dv = env.CreateDataView(new TSrc[0]);
             _engine = env.CreatePredictionEngine<TSrc, TDst>(pipe.Transform(dv));
         }