'Constructor.
The arguments are two RawIO instances.'

def __init__(self, reader, writer, buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):

    if (max_buffer_size is not None):
        warnings.warn(u'max_buffer_size    is    deprecated', DeprecationWarning, 2)
    if (not reader.readable()):
        raise IOError(u'"reader"    argument    must    be    readable.')
    if (not writer.writable()):
        raise IOError(u'"writer"    argument    must    be    writable.')
    self.reader = BufferedReader(reader, buffer_size)
    self.writer = BufferedWriter(writer, buffer_size)
