Trigger the after_save hook on documents, if present.

def trigger(self, event, filter=None, update=None, documents=None, ids=None, replacements=None):
        """ Trigger the after_save hook on documents, if present. """

        if not self.has_trigger(event):
            return

        if documents is not None:
            pass
        elif ids is not None:
            documents = self.find_by_ids(ids, read_use="primary")
        elif filter is not None:
            documents = self.find(filter, read_use="primary")
        else:
            raise Exception("Trigger couldn't filter documents")

        for doc in documents:
            getattr(doc, event)(update=update, replacements=replacements)