code: def test_dct_backend(self, xp, dtype):
      backend = "scipy" if xp is np else cp_fft
      with scipy_fft.set_backend(backend):
          fft_func = getattr(scipy_fft, self.function)
          return self._run_transform(fft_func, xp, dtype)
  
file_path: cupy/tests/cupyx_tests/scipy_tests/fft_tests/test_realtransforms.py
imports: import numpy
  import pytest
  from cupyx.scipy import fft
  from cupy import testing
label_desc: Use image node_id 3 for calling the TestDctDst obj's underlying member method code with example usage: obj.test_dct_backend(xp, dtype) and returns: self