code: def check_required(config):
      
      if config.get('domain_key') is None:
          raise CfgError("The domain_key option is required")
      if config.get('remote_loc') is None:
          raise CfgError("The remote_location option is required")
      if config.get('gpg_keyid') is None:
          raise CfgError("The gpg_keyid option is required")
docs: Validate the input