code: def test_difference_freq(self, sort):
      # GH14323: difference of Period MUST preserve frequency
      # but the ability to union results must be preserved
  
      index = period_range("20160920", "20160925", freq="D")
  
      other = period_range("20160921", "20160924", freq="D")
      expected = PeriodIndex(["20160920", "20160925"], freq="D")
      idx_diff = index.difference(other, sort)
      tm.assert_index_equal(idx_diff, expected)
      tm.assert_attr_equal("freq", idx_diff, expected)
  
      other = period_range("20160922", "20160925", freq="D")
      idx_diff = index.difference(other, sort)
      expected = PeriodIndex(["20160920", "20160921"], freq="D")
      tm.assert_index_equal(idx_diff, expected)
      tm.assert_attr_equal("freq", idx_diff, expected)
  
file_path: pandas/pandas/tests/indexes/period/test_setops.py
imports: import numpy
  import pytest
  import pandas
  from pandas import PeriodIndex, date_range, period_range
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestPeriodIndex obj's underlying member method code with example usage: obj.test_difference_freq(sort) without return types