docs: def source_attr(attr_name):
      """
      Creates a setter that will set the specified source attribute
      to the current value.
      @param attr_name: the name of an attribute belonging to the source.
      @type attr_name: str
      """
  
      def source_attr(value, context, **_params):
          setattr(context["model"].source, attr_name, value)
          return _attr()
  
      return source_attr