docs: function(arr, iterator) {
  			if (typeof iterator !== 'function') return apiRejection('iterator must be a function');
  
  			var self = this;
  			var i = 0;
  			return Promise.resolve().then(function iterate() {
  				if (i == arr.length) return;
  
  				return Promise.resolve(iterator.call(self, arr[i]))
  				.then(function(result) {
  					if (result !== undefined) return result;
  
  					i++;
  					return iterate();
  				});
  			});
  		}