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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 handle_wiki(msg):
 """ Given a wiki message, return the FAS username. """


    if 'wiki.article.edit' in msg.topic:
        username = msg.msg['user']
    elif 'wiki.upload.complete' in msg.topic:
        username = msg.msg['user_text']
    else:
        raise ValueError("Unhandled topic.")

    return username