code: private String doFindEquivalence(final String sourceNamespace,
              final String destinationNamespace, final String sourceValue) {
          JDBMEquivalenceLookup sourceLookup =
                  openEquivalences.get(sourceNamespace);
          if (sourceLookup == null) {
              return null;
          }
          final SkinnyUUID sourceUUID = sourceLookup.lookup(sourceValue);
  
          if (sourceUUID == null) {
              return null;
          }
          return doFindEquivalence(destinationNamespace, sourceUUID);
      }
docs: Obtain the destinationNamespace equivalent value of sourceValue in sourceNamespace
  @param sourceNamespace resourceLocation of source namespace
  @param destinationNamespace resourceLocation of destination namespace
  @param sourceValue
  @return equivalent value, may be null.