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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 join(tokens, start, result):
 """Join tokens into a single string with spaces between."""

    texts = []
    if len(result) > 0:
        for e in result:
            for child in e.iter():
                if child.text is not None:
                    texts.append(child.text)
        return [E(result[0].tag, ' '.join(texts))]