code: protected function getConnection()
      {
          if (null === $this->connection) {
              // @codingStandardsIgnoreStart
              @trigger_error(
                  'Connection is missing in class ' . static::class .
                  '. The automatic fallback will be dropped in MetaModels 3.0. Please use dependency injection',
                  E_USER_DEPRECATED
              );
              // @codingStandardsIgnoreEnd
              return $this->connection = System::getContainer()->get('database_connection');
          }
  
          return $this->connection;
      }
docs: Retrieve the connection.
  
  @return Connection