code: def schema_helper(self, name, _, schema=None, **kwargs):
          
          if schema is None:
              return None
  
          schema_instance = resolve_schema_instance(schema)
  
          schema_key = make_schema_key(schema_instance)
          self.warn_if_schema_already_in_spec(schema_key)
          self.openapi.refs[schema_key] = name
  
          json_schema = self.openapi.schema2jsonschema(schema_instance)
  
          return json_schema
docs: Definition helper that allows using a marshmallow
          :class:`Schema <marshmallow.Schema>` to provide OpenAPI
          metadata.
  
          :param type|Schema schema: A marshmallow Schema class or instance.