code: function indexExists(coll, indexes, options, callback) {
    indexInformation(coll, options, (err, indexInformation) => {
      // If we have an error return
      if (err != null) return handleCallback(callback, err, null);
      // Let's check for the index names
      if (!Array.isArray(indexes))
        return handleCallback(callback, null, indexInformation[indexes] != null);
      // Check in list of indexes
      for (let i = 0; i < indexes.length; i++) {
        if (indexInformation[indexes[i]] == null) {
          return handleCallback(callback, null, false);
        }
      }
  
      // All keys found return true
      return handleCallback(callback, null, true);
    });
  }
docs: Check if one or more indexes exist on the collection. This fails on the first index that doesn't exist.
  
  @method
  @param {Collection} a Collection instance.
  @param {(string|array)} indexes One or more index names to check.
  @param {Object} [options] Optional settings. See Collection.prototype.indexExists for a list of options.
  @param {Collection~resultCallback} [callback] The command result callback