code: def verify_fft_options(opt, parser):
      
  
      if len(opt.fft_backends) > 0:
          _all_backends = get_backend_names()
          for backend in opt.fft_backends:
              if backend not in _all_backends:
                  parser.error("Backend {0} is not available".format(backend))
  
      for backend in get_backend_modules():
          try:
              backend.verify_fft_options(opt, parser)
          except AttributeError:
              pass
docs: Parses the FFT options and verifies that they are
         reasonable.
  
      Parameters
      ----------
      opt : object
          Result of parsing the CLI with OptionParser, or any object with the
          required attributes.
      parser : object
          OptionParser instance.