src/Rbac/Migrations/m170907_052038_rbac_add_index_on_auth_assignment_user_id.php
public function safeDown(ConnectionInterface $connection)
    {
        $authManager = $this->getAuthManager();
        return $this->dropIndex($this->index, $authManager->assignmentTable);
    }
public function safeDown(ConnectionInterface $connection)
    {
        $authManager = $this->getAuthManager();
        return $this->dropIndex($this->index, $authManager->assignmentTable);
    }
{@inheritdoc}