How to use the geventhttpclient._parser.HTTPResponseParser function in geventhttpclient

def copy(data):
    if six.PY3:
        return data[:]
    else:
        return str(data)


class HTTPConnectionClosed(HTTPParseError):
    pass


class HTTPProtocolViolationError(HTTPParseError):
    pass


class HTTPResponse(HTTPResponseParser):

    def __init__(self, method='GET', headers_type=Headers):
        super(HTTPResponse, self).__init__()
        self.method = method.upper()
        self.headers_complete = False
        self.message_begun = False
        self.message_complete = False
        self._headers_index = headers_type()
        self._header_state = HEADER_STATE_INIT
        self._current_header_field = None
        self._current_header_value = None
        self._header_position = 1
        self._body_buffer = bytearray()
        self.status_message = None

    def __getitem__(self, key):