code: function size($queue = null)
      {
          try {
              $count = $this->collection->count(
                  [
                      'queue' => $this->_normalizeQueueName($queue),
                  ]
              );
          } catch (\Exception $e) {
              throw new exReadError('Error While Write To Mongo Client.', $e->getCode(), $e);
          }
  
          return $count;
      }
docs: Get Queue Size
  
  @param string $queue
  
  @return int
  @throws exIOError