code: def stringify
        if GenerateResult.wanted_attributes(event).include?(:defined_class)
          self.defined_class = defined_class.to_s
        end
        if GenerateResult.wanted_attributes(event).include?(:return_value)
          if return_value.nil? or return_value.is_a? Symbol or
            # ActiveRecord::ConnectionAdapters::Column override method ==
            (return_value.is_a? String and return_value == '')
            self.return_value = return_value.inspect
          else
            self.return_value = return_value.to_s
          end
        end
        self.event = event.to_s
        self.method_id = method_id.to_s
        self
      end
docs: todo: this is a mutable method
   not a good solution.
   we should use it on the return hash of method to_hash