def put(key, overwrite=False):
    """
        Function generator to put a specific key/value pair in a node.

        :param key: The key to access from the node.
        :type key: str
        :return: Binary function with signature func(node: Node, value) -> None
        """
    def func(node, value):
        if (key not in node.contents) or overwrite:
            node.contents[key] = value
    return func