docs: def show(modifier):
      '''
      Show filter parameters.
  
      modifier:
          Modifier to apply for filtering. Only a useful subset of what pfctl supports
          can be used with Salt.
  
          - rules
          - states
          - tables
  
      CLI example:
  
      .. code-block:: bash
  
          salt '*' pf.show rules
      '''
      # By definition showing the parameters makes no changes.
      ret = {'changes': False}
  
      capital_modifiers = ['Tables']
      all_modifiers = ['rules', 'states', 'tables']
      all_modifiers += capital_modifiers
      if modifier.title() in capital_modifiers:
          modifier = modifier.title()
  
      if modifier not in all_modifiers:
          raise SaltInvocationError('Unknown modifier: {0}'.format(modifier))
  
      cmd = 'pfctl -s {0}'.format(modifier)
      result = __salt__['cmd.run_all'](cmd,
                                       output_loglevel='trace',
                                       python_shell=False)
  
      if result['retcode'] == 0:
          ret['comment'] = result['stdout'].split('\n')
      else:
          raise CommandExecutionError(
              'Could not show {0}'.format(modifier),
              info={'errors': [result['stderr']], 'changes': False}
          )
  
      return ret