code: func FieldByIndexGetter(index []int) Getter {
  	return func(s reflect.Value) []reflect.Value {
  		vals := valueSlice(s.Len())
  		for i := range vals {
  			vals[i] = reflect.Indirect(reflect.Indirect(s.Index(i)).FieldByIndex(index))
  		}
  		return vals
  	}
  }
docs: // Returns a Getter which gets nested fields corresponding to e.g.
  // []int{1, 2, 3} = field 3 of field 2 of field 1 of each struct from a
  // reflect.Value for a slice of a struct type, returning them as a slice of
  // reflect.Value (one Value for each of the indices in the structs.) Can be
  // used with Sort to sort an []Object by the first field in the struct
  // value of the first field of each Object. A runtime panic will occur if
  // the specified field isn't exported.