hasAtomics() {
    if (!utils.isPOJO(this[arrayAtomicsSymbol])) {
      return 0;
    }

    return Object.keys(this[arrayAtomicsSymbol]).length;
  }
Returns the number of pending atomic operations to send to the db for this array.

@api private
@return {Number}
@method hasAtomics
@memberOf MongooseArray