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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 read(self, length, timeout):
 """Read 'length' bytes from this stream transport. Args: length: If not 0, read this many bytes from the stream, otherwise read all available data (at least one byte). timeout: timeouts.PolledTimeout to use for this read operation. Returns: The bytes read from this stream. """

    self._read_messages_until_true(
        lambda: self._buffer_size and self._buffer_size >= length, timeout)

    with self._read_buffer_lock:
      data, push_back = ''.join(self._read_buffer), ''
      if length:
        data, push_back = data[:length], data[length:]
      self._read_buffer.clear()
      self._buffer_size = len(push_back)
      if push_back:
        self._read_buffer.appendleft(push_back)
    return data