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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 get_sender(doc):
 """Get the key_id from the `sig` element which contains urlsafe_b64encoded Diaspora handle. :param doc: ElementTree document :returns: Diaspora handle """

        key_id = doc.find(".//{%s}sig" % NAMESPACE).get("key_id")
        return urlsafe_b64decode(key_id).decode("utf-8")