code: def serialize(self, data=None):
          
          if data is not None and self.response is not None:
              # Set the content type.
              self.response['Content-Type'] = self.media_types[0]
  
              # Write the encoded and prepared data to the response.
              self.response.write(data)
  
          # Return the serialized data.
          # This has normally been transformed by a base class.
          return data
docs: Transforms the object into an acceptable format for transmission.
  
          @throws ValueError
              To indicate this serializer does not support the encoding of the
              specified object.