code: public function loadMany($keys)
      {
          if (!is_array($keys) && !$keys instanceof \Traversable) {
              throw new \InvalidArgumentException(sprintf('The "%s" method must be called with Array<key> but got: %s.', __METHOD__, gettype($keys)));
          }
          return $this->getPromiseAdapter()->createAll(array_map(
              function ($key) {
                  return $this->load($key);
              },
              $keys
          ));
      }
docs: {@inheritdoc}