code: public Set<String> getNeverGroupedIds() {
          String s = props.getProperty("neverGroupedIds");
          if(s == null) return Collections.emptySet();
          
          Set<String> res = new HashSet<String>();
          String[] parts = s.split("[,]");
          for(String part : parts) {
              res.add(part);
          }
          return res;
      }
docs: Returns the set of ids of SNOMED roles that should never be placed in a
  role group.
  
  @return Set of ids of SNOMED roles that should never be placed in a role
  group.