code: public DocumentTranslationRequestDataChangeSet setTargetLanguagesMap(
              Map<String, Map<String, Set<String>>> targetLanguagesMap) {
          // TODO - check empty map?
          if (targetLanguagesMap == null) {
              throw new NullPointerException("The input map is null.");
          }
          this.targetLanguagesMap = targetLanguagesMap;
          return this;
      }
docs: Sets a map containing target languages indexed by document ids. This method adopts
  the input map without creating a safe copy.
  
  @param targetLanguagesMap   A map containing target languages indexed by
  document ids.
  @return  This object.
  @throws NullPointerException When the input <code>targetLanguagesMap</code> is null.