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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 comment_from_tag(tag):
 """ Convenience function to create a full-fledged comment for a given tag, for example it is convenient to assign a Comment to a ReturnValueSymbol. """

    if not tag:
        return None
    comment = Comment(name=tag.name,
                      meta={'description': tag.description},
                      annotations=tag.annotations)
    return comment