def __init__(self, **kwargs):
super(Session, self).__init__(**kwargs)<EOL>self._check_packers()<EOL>self.none = self.pack({})<EOL>self.session<EOL>
create a Session object

        Parameters
        ----------

        debug : bool
            whether to trigger extra debugging statements
        packer/unpacker : str : 'json', 'pickle' or import_string
            importstrings for methods to serialize message parts.  If just
            'json' or 'pickle', predefined JSON and pickle packers will be used.
            Otherwise, the entire importstring must be used.

            The functions must accept at least valid JSON input, and output
            *bytes*.

            For example, to use msgpack:
            packer = 'msgpack.packb', unpacker='msgpack.unpackb'
        pack/unpack : callables
            You can also set the pack/unpack callables for serialization
            directly.
        session : unicode (must be ascii)
            the ID of this Session object.  The default is to generate a new
            UUID.
        bsession : bytes
            The session as bytes
        username : unicode
            username added to message headers.  The default is to ask the OS.
        key : bytes
            The key used to initialize an HMAC signature.  If unset, messages
            will not be signed or checked.
        keyfile : filepath
            The file containing a key.  If this is set, `key` will be
            initialized to the contents of the file.