fix linting error

Author: margaret

Diff for: pandas/tests/indexing/test_loc.py

@@ -644,7 +644,7 @@ def test_identity_slice_returns_new_object(self):
         # These should not return copies
         assert original_df is original_df.loc[:, :]
         df = DataFrame(np.random.randn(10, 4))
-        assert df[0] is df.loc[:,0]
+        assert df[0] is df.loc[:, 0]
 
         # Same tests for Series
         original_series = Series([1, 2, 3, 4, 5, 6])