def drop_foreign(self, index):
        return self._drop_index_command('drop_foreign', 'foreign', index)
Used by actor (owner) to check number of token slots available on the port.
dataset/ETHPy150Open sdispater/orator/orator/schema/blueprint.py/Blueprint.drop_foreign--crossover with--dataset/ETHPy150Open EricssonResearch/calvin-base/calvin/actor/actorport.py/OutPort.available_tokens