code: private Map<String, Field> getFieldsbyid() {
          if (fieldsbyid == null) {
              fieldsbyid = new HashMap<String, Field>();
              for (Field f : getAllFields()) {
                  fieldsbyid.put(f.getId(), f);
              }
          }
          return fieldsbyid;
      }
docs: Getter for fieldsbyid. If its null, this methods fill it
  
  @return The mapped field list