code: def first_phase(invec, outvec, N1, N2):
      
      global _theplan
      if _theplan is None:
          _theplan = plan_first_phase(N1, N2)
      fexecute(_theplan, invec.ptr, outvec.ptr)
docs: This implements the first phase of the FFT decomposition, using
      the standard FFT many plans.
  
      Parameters
      -----------
      invec : array
          The input array.
      outvec : array
          The output array.
      N1 : int
          Number of rows.
      N2 : int
          Number of columns.