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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 multi(stream):
 """ Internal multiplexer for multiplex_detect. :type stream: obspy.core.stream.Stream :param stream: Stream to multiplex :return: trace of multiplexed data :rtype: obspy.core.trace.Trace .. Note: Requires all channels to be the same length. Maps a standard multiplexed stream of seismic data to a single traces of \ multiplexed data as follows: Input: Output: """

    stack = stream[0].data
    for tr in stream[1:]:
        stack = np.dstack(np.array([stack, tr.data]))
    multiplex = stack.reshape(stack.size, )
    return multiplex