def _get_eager_model_keys(self, models):
        keys = []

        for model in models:
            value = getattr(model, self._foreign_key)

            if value is not None and value not in keys:
                keys.append(value)

        if not len(keys):
            return [0]

        return keys
:param key_type: a column class indicating the types of the key
dataset/ETHPy150Open sdispater/orator/orator/orm/relations/belongs_to.py/BelongsTo._get_eager_model_keys--crossover with--dataset/ETHPy150Open datastax/python-driver/cassandra/cqlengine/columns.py/Map.__init__