def peek_step(self, val: ObjectValue,
                  sn: "DataNode") -> Tuple[Value, "DataNode"]:
        """Return member value addressed by the receiver + its schema node.

        Args:
            val: Current value (object).
            sn:  Current schema node.
        """
        cn = sn.get_data_child(self.name, self.namespace)
        try:
            return (val[cn.iname()], cn)
        except (IndexError, KeyError, TypeError):
            return (None, cn)
Return member value addressed by the receiver + its schema node.

        Args:
            val: Current value (object).
            sn:  Current schema node.