code: public static Datasubtype isValid(Datatype datatype, Set<Datasubtype> datasubtypes, String code) {
          Map<Datasubtype, ValiditySet> subtable = ValidityData.data.get(datatype);
          if (subtable != null) {
              for (Datasubtype datasubtype : datasubtypes) {
                  ValiditySet validitySet = subtable.get(datasubtype);
                  if (validitySet != null) {
                      if (validitySet.contains(AsciiUtil.toLowerString(code))) {
                          return datasubtype;
                      }
                  }
              }
          }
          return null;
      }
docs: Returns the Datasubtype containing the code, or null if there is none.