code: def test_boxplot_return_type_none(self, hist_df):
      # GH 12216; return_type=None & by=None -> axes
      result = hist_df.boxplot()
      assert isinstance(result, mpl.pyplot.Axes)
  
imports: import itertools
  import string
  import numpy
  import pytest
  from pandas import DataFrame, MultiIndex, Series, date_range, plotting, timedelta_range
  import pandas._testing
  from pandas.tests.plotting.common import _check_axes_shape, _check_box_return_type, _check_plot_works, _check_ticks_props, _check_visible
  from pandas.io.formats.printing import pprint_thing
label_desc: Use image node_id 9 for calling the TestDataFramePlots obj's underlying member method code with example usage: obj.test_boxplot_return_type_none(hist_df) without return types