This code ``` import pandas from datetime import datetime df1 = pandas.DataFrame({'a': []}) df2 = pandas.DataFrame({'a': []}) df1['a'] = pandas.to_datetime(df1['a']) pandas.testing.assert_frame_equal(df1, df2, check_dtype=False) ``` raises: ``` AssertionError: right is not an ExtensionArray ``` But should it raise instead no exception as df1 and df2 are identical, except for their dtypes ?