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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def after(self, *nodes: Union[AbstractNode, str]) -> None: """Append nodes after this node. If nodes contains ``str``, it will be converted to Text node. """

        if self.parentNode:
            node = _to_node_list(nodes)
            _next_node = self.nextSibling
            if _next_node is None:
                self.parentNode.appendChild(node)
            else:
                self.parentNode.insertBefore(node, _next_node)