code: def fft_transpose_fftw(vec):
      
      global _thetransposeplan
      outvec = pycbc.types.zeros(len(vec), dtype=vec.dtype)
      if _theplan is None:
          N1, N2 = splay(vec)
          _thetransposeplan = plan_transpose(N1, N2)
      ftexecute(_thetransposeplan, vec.ptr, outvec.ptr)
      return  outvec
docs: Perform an FFT transpose from vec into outvec.
      (Alex to provide more details in a write-up.)
  
      Parameters
      -----------
      vec : array
          Input array.
  
      Returns
      --------
      outvec : array
          Transposed output array.