code: def _call_pyfftw(self, x, out, **kwargs):
          
          assert isinstance(x, np.ndarray)
          assert isinstance(out, np.ndarray)
  
          kwargs.pop('normalise_idft', None)  # Using `False` here
          kwargs.pop('axes', None)
          kwargs.pop('halfcomplex', None)
          flags = list(_pyfftw_to_local(flag) for flag in
                       kwargs.pop('flags', ('FFTW_MEASURE',)))
          try:
              flags.remove('unaligned')
          except ValueError:
              pass
          try:
              flags.remove('destroy_input')
          except ValueError:
              pass
          effort = flags[0] if flags else 'measure'
  
          direction = 'forward' if self.sign == '-' else 'backward'
          self._fftw_plan = pyfftw_call(
              x, out, direction=direction, axes=self.axes,
              halfcomplex=self.halfcomplex, planning_effort=effort,
              fftw_plan=self._fftw_plan, normalise_idft=False)
  
          return out
docs: Implement ``self(x[, out, **kwargs])`` using pyfftw.
  
          Parameters
          ----------
          x : `numpy.ndarray`
              Input array to be transformed
          out : `numpy.ndarray`
              Output array storing the result
          flags : sequence of strings, optional
              Flags for the transform. ``'FFTW_UNALIGNED'`` is not
              supported, and ``'FFTW_DESTROY_INPUT'`` is enabled by
              default. See the `pyfftw API documentation`_
              for futher information.
              Default: ``('FFTW_MEASURE',)``
          threads : positive int, optional
              Number of threads to use. Default: 1
          planning_timelimit : float or ``None``, optional
              Rough upper limit in seconds for the planning step of the
              transform. ``None`` means no limit. See the
              `pyfftw API documentation`_ for futher information.
  
          Returns
          -------
          out : `numpy.ndarray`
              Result of the transform. If ``out`` was given, the returned
              object is a reference to it.
  
          References
          ----------
          .. _pyfftw API documentation:
             https://pyfftw.readthedocs.io