code: def insert_fft_option_group(parser):
      
      fft_group = parser.add_argument_group("Options for selecting the"
                                            " FFT backend and controlling its performance"
                                            " in this program.")
      # We have one argument to specify the backends.  This becomes the default list used
      # if none is specified for a particular call of fft() of ifft().  Note that this
      # argument expects a *list* of inputs, as indicated by the nargs='*'.
      fft_group.add_argument("--fft-backends",
                        help="Preference list of the FFT backends. "
                             "Choices are: \n" + str(get_backend_names()),
                        nargs='*', default=[])
  
      for backend in get_backend_modules():
          try:
              backend.insert_fft_options(fft_group)
          except AttributeError:
              pass
docs: Adds the options used to choose an FFT backend. This should be used
      if your program supports the ability to select the FFT backend; otherwise
      you may simply call the fft and ifft functions and rely on default
      choices.  This function will also attempt to add any options exported
      by available backends through a function called insert_fft_options.
      These submodule functions should take the fft_group object as argument.
  
      Parameters
      ----------
      parser : object
          OptionParser instance