reference issue in tests, clarify default in docstring

Author: hoffmann

pandas/io/parquet.py

@@ -188,7 +188,7 @@ def read_parquet(path, engine='auto', columns=None, **kwargs):
     ----------
     path : string
         File path
-    columns: list
+    columns: list, default=None
         If not None, only these columns will be read from the file.
     engine : {'auto', 'pyarrow', 'fastparquet'}, default 'auto'
         Parquet reader library to use. If 'auto', then the option

pandas/tests/io/test_parquet.py

@@ -283,6 +283,7 @@ def test_compression(self, engine, compression):
         self.check_round_trip(df, engine, compression=compression)
 
     def test_read_columns(self, engine, fp):
+        #GH18154
         df = pd.DataFrame({'string': list('abc'),
                            'int': list(range(1, 4))})