code: def verify_ethinca_metric_options(opts, parser):
      
      if opts.filter_cutoff is not None and not (opts.filter_cutoff in
                pnutils.named_frequency_cutoffs.keys()):
          parser.error("Need a valid cutoff formula to calculate ethinca or "
                       "assign filter f_final values! Possible values are "
                       +str(pnutils.named_frequency_cutoffs.keys()))
      if (opts.calculate_ethinca_metric or opts.calculate_time_metric_components)\
                                             and not opts.ethinca_frequency_step:
          parser.error("Need to specify a cutoff frequency step to calculate "
                       "ethinca!")
      if not (opts.calculate_ethinca_metric or\
                opts.calculate_time_metric_components) and opts.ethinca_pn_order:
          parser.error("Can't specify an ethinca PN order if not "
                       "calculating ethinca metric!")
docs: Checks that the necessary options are given for the ethinca metric
      calculation.
  
      Parameters
      ----------
      opts : argparse.Values instance
          Result of parsing the input options with OptionParser
      parser : object
          The OptionParser instance.