'Return a list of tuples of (state, obj)
for all objects in this attribute\'s current state
+ history.
Only applies to object-based attributes.
This is an inlining of existing functionality
which roughly corresponds to:
get_state_history(
state,
key,
passive=PASSIVE_NO_INITIALIZE).sum()'

def get_all_pending(self, state, dict_):

    raise NotImplementedError()
