def METHOD_NAME(self, data):
    """
    Add more data to the frame buffer.
    :param data: A bytestring containing the byte buffer.
    """
    if self._preamble_len:
        data_len = len(data)
        of_which_preamble = min(self._preamble_len, data_len)
        if self._preamble[:of_which_preamble] != data[:of_which_preamble]:
            raise ProtocolError("Invalid HTTP/2 preamble.")
        data = data[of_which_preamble:]
        self._preamble_len -= of_which_preamble
        self._preamble = self._preamble[of_which_preamble:]
    self.data += data