docs: def output(self, value):
          """SPL output port assignment expression.
  
          Arguments:
              value(str): SPL expression used for an output assignment. This can be a string, a constant, or an :py:class:`Expression`.
  
          Returns:
              Expression: Output assignment expression that is valid as a the context of this operator.
          """
          return super(Source, self).output(self.stream, value)