code: func (s *SortFilter) NumDecreasing(n int) *SortFilter {
  	return s.Num(n).flipLast()
  }
docs: // NumDecreasing sets the next sort key to sort by column n in reverse
  // numeric order. Column 0 means the entire string. Items that do not
  // have column n sort to the end.  Items whose column n is not a
  // number sort to the front.