code: def test_shallow_copy_disallow_i8(self):
      # GH#24391
      pi = period_range("2018-01-01", periods=3, freq="2D")
      with pytest.raises(AssertionError, match="ndarray"):
          pi._shallow_copy(pi.asi8)
  
imports: import numpy
  import pytest
  from pandas._libs.tslibs.period import IncompatibleFrequency
  from pandas.core.dtypes.dtypes import PeriodDtype
  from pandas import Index, NaT, Period, PeriodIndex, Series, date_range, offsets, period_range
  import pandas._testing
  from pandas.core.arrays import PeriodArray
label_desc: Use image node_id 2 for calling the TestShallowCopy obj's underlying member method code with example usage: obj.test_shallow_copy_disallow_i8() without return types