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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 innertext(node):
 """Return the inner text of a node. If a node has no sub elements, this is just node.text. Otherwise, it's node.text + sub-element-text + node.tail."""

    if not len(node):
        return node.text

    return (node.text or '') + ''.join([etree.tostring(c) for c in node]) + (node.tail or '')