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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 maybe_stream(s):
 """Ensure that the given argument is a stream."""

    if isinstance(s, Stream):
        return s

    if s is None:
        stream = InMemStream()
        stream.close()  # we don't intend to write anything
        return stream

    if isinstance(s, unicode):
        s = s.encode('utf-8')
    if isinstance(s, bytearray):
        s = bytes(s)

    if isinstance(s, bytes):
        stream = InMemStream(s)
        stream.close()  # we don't intend to write anything
        return stream

    # s may still conform to the Stream interface. Yay duck typing.
    return s