public function getForeignKeys()
    {
        $return = [];
        $table = $this->getName();

        /** @var Base $call */
        foreach ($this->getGenericCalls() as $call) {
            if (isset($call->on) && $call->on !== $table) {
                $return[(string)$call->on] = $call;
            } // if
        } // foreach

        return $return;
    }