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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_trace_id_from_flask():
 """Get trace_id from flask request headers. :rtype: str :returns: TraceID in HTTP request headers. """

    if flask is None or not flask.request:
        return None

    header = flask.request.headers.get(_FLASK_TRACE_HEADER)

    if header is None:
        return None

    trace_id = header.split("/", 1)[0]

    return trace_id