def prepare(self, object):
        """
        (internal) Create a list for persisting an object to.  This will allow
        backreferences to be made internal to the object. (circular
        references).

        The reason this needs to happen is that we don't generate an ID for
        every object, so we won't necessarily know which ID the object will
        have in the future.  When it is 'cooked' ( see _cook ), it will be
        assigned an ID, and the temporary placeholder list created here will be
        modified in-place to create an expression that gives this object an ID:
        [reference id# [object-jelly]].
        """

        # create a placeholder list to be preserved
        self.preserved[id(object)] = []
        # keep a reference to this object around, so it doesn't disappear!
        # (This isn't always necessary, but for cases where the objects are
        # dynamically generated by __getstate__ or getStateToCopyFor calls, it
        # is; id() will return the same value for a different object if it gets
        # garbage collected.  This may be optimized later.)
        self.cooker[id(object)] = object
        return []

        (internal) Create a list for persisting an object to.  This will allow
        backreferences to be made internal to the object. (circular
        references).

        The reason this needs to happen is that we don't generate an ID for
        every object, so we won't necessarily know which ID the object will
        have in the future.  When it is 'cooked' ( see _cook ), it will be
        assigned an ID, and the temporary placeholder list created here will be
        modified in-place to create an expression that gives this object an ID:
        [reference id# [object-jelly]].
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/jelly.py