code: def insert_fft_options(optgroup):
      
      optgroup.add_argument("--fftw-measure-level",
                        help="Determines the measure level used in planning "
                             "FFTW FFTs; allowed values are: " + str([0,1,2,3]),
                        type=int, default=_default_measurelvl)
      optgroup.add_argument("--fftw-threads-backend",
                        help="Give 'openmp', 'pthreads' or 'unthreaded' to specify which threaded FFTW to use",
                        default=None)
      optgroup.add_argument("--fftw-input-float-wisdom-file",
                        help="Filename from which to read single-precision wisdom",
                        default=None)
      optgroup.add_argument("--fftw-input-double-wisdom-file",
                        help="Filename from which to read double-precision wisdom",
                        default=None)
      optgroup.add_argument("--fftw-output-float-wisdom-file",
                        help="Filename to which to write single-precision wisdom",
                        default=None)
      optgroup.add_argument("--fftw-output-double-wisdom-file",
                        help="Filename to which to write double-precision wisdom",
                        default=None)
      optgroup.add_argument("--fftw-import-system-wisdom",
                            help = "If given, call fftw[f]_import_system_wisdom()",
                            action = "store_true")
docs: Inserts the options that affect the behavior of this backend
  
      Parameters
      ----------
      optgroup: fft_option
         OptionParser argument group whose options are extended