code: def test_cffi(self):
      bit_generator = self.bit_generator(*self.data1["seed"])
      cffi_interface = bit_generator.cffi
      assert isinstance(cffi_interface, interface)
      other_cffi_interface = bit_generator.cffi
      assert other_cffi_interface is cffi_interface
  
imports: import os
  from os.path import join
  import sys
  import numpy
  from numpy.testing import assert_equal, assert_allclose, assert_array_equal, assert_raises
  import pytest
  from numpy.random import Generator, MT19937, PCG64, PCG64DXSM, Philox, RandomState, SeedSequence, SFC64, default_rng
  from numpy.random._common import interface
label_desc: Use image node_id 16 for calling the Base obj's underlying member method code with example usage: obj.test_cffi() without return types