'Notify that a entity has been removed from the collection.
Initiator is the InstrumentedAttribute that initiated the membership
mutation, and should be left as None unless you are passing along
an initiator value from a chained operation.'

def fire_remove_event(self, item, initiator=None):

    if (initiator is not False):
        if self.invalidated:
            self._warn_invalidated()
        self.attr.fire_remove_event(self.owner_state, self.owner_state.dict, item, initiator)
