code: def _collect_valid_settings(meta, clsdict):
          
          enum_members = clsdict['__members__']
          valid_settings = []
          for member in enum_members:
              valid_settings.extend(member.valid_settings)
          clsdict['_valid_settings'] = valid_settings
docs: Return a sequence containing the enumeration values that are valid
          assignment values. Return-only values are excluded.