code: def field2pattern(self, field, **kwargs):
          
          regex_validators = (
              v
              for v in field.validators
              if isinstance(getattr(v, "regex", None), RegexType)
          )
          v = next(regex_validators, None)
          attributes = {} if v is None else {"pattern": v.regex.pattern}
  
          if next(regex_validators, None) is not None:
              warnings.warn(
                  "More than one regex validator defined on {} field. Only the "
                  "first one will be used in the output spec.".format(type(field)),
                  UserWarning,
              )
  
          return attributes
docs: Return the dictionary of OpenAPI field attributes for a set of
          :class:`Range <marshmallow.validators.Regexp>` validators.
  
          :param Field field: A marshmallow field.
          :rtype: dict