func (is IdentifierSlice) Less(i, j int) bool {
	return is[i].ID() < is[j].ID()
}
func (is IdentifierSlice) Less(i, j int) bool {
	return is[i].ID() < is[j].ID()
}
func ( is IdentifierSlice ) Less ( i , j int ) bool { return is [ i ] . ID ( ) < is [ j ] . ID ( ) }
// Less will return true if the ID of element at i is less than j;
// part of the sort.Interface
Less will return true if the ID of element at i is less than j ; part of the sort . Interface