'Validate that this type of authentication is supported
:param spec.Connection.Start start: Connection.Start method
:rtype: tuple(str|None, str|None)'

def response_for(self, start):

    if (as_bytes(PlainCredentials.TYPE) not in as_bytes(start.mechanisms).split()):
        return (None, None)
    return (PlainCredentials.TYPE, ((('\x00' + as_bytes(self.username)) + '\x00') + as_bytes(self.password)))
