code: def test_df_dates(self):
      result = self.utils.df_dates(self.data)
      self.assertEqual(None, result)
  
      result = self.utils.df_dates(self.data, "1999-11-01")
      self.assertEqual(1, result.shape[0])
  
      result = self.utils.df_dates(
          self.data,
          [
              "1999-11-01",
              "2020-08-15",
              "2020-08-24",
              "2020-08-25",
              "2020-08-26",
              "2020-08-27",
          ],
      )
      self.assertEqual(5, result.shape[0])
  
imports: from .config import sample_data
  from .context import pandas_ta
  from unittest import skip, TestCase
  from unittest.mock import patch
  import numpy
  import numpy.testing
  from pandas import DataFrame, Series
  from pandas.api.types import is_datetime64_ns_dtype, is_datetime64tz_dtype
label_desc: Use image node_id 14 for calling the TestUtilities obj's underlying member method code with example usage: obj.test_df_dates() without return types