def feed(self, data):
        """
        Consume a chunk of data and attempt to parse it.

        @param data: A bytestring.
        @type data: bytes

        @return: A two-tuple containing, in order, an L{IProxyInfo} and any
            bytes fed to the parser that followed the end of the header.  Both
            of these values are None until a complete header is parsed.

        @raises InvalidProxyHeader: If the bytes fed to the parser create an
            invalid PROXY header.
        """

        Consume a chunk of data and attempt to parse it.

        @param data: A bytestring.
        @type data: bytes

        @return: A two-tuple containing, in order, an L{IProxyInfo} and any
            bytes fed to the parser that followed the end of the header.  Both
            of these values are None until a complete header is parsed.

        @raises InvalidProxyHeader: If the bytes fed to the parser create an
            invalid PROXY header.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/haproxy/_interfaces.py