docs: function(item, index) {
                  var n = this.length,
                          i = index == null ? n - 1 : index
                  if (i < 0)
                      i = Math.max(0, n + i)
                  for (; i >= 0; i--)
                      if (this[i] === item)
                          return i
                  return -1
              }