code: public static TextCorpusStored compose(String lang, TextCorpusLayerStoredAbstract... layers) {
          TextCorpusStored tc = new TextCorpusStored(lang);
          for (TextCorpusLayerStoredAbstract layer : layers) {
              tc.layersInOrder[TextCorpusLayerTag.getFromClass(layer.getClass()).ordinal()] = layer;
          }
          tc.connectLayers();
          return tc;
      }
docs: Composes the layers into one document. Normally, you should not use this
  method, unless you want to manually compose document from the layer
  pieces.The method composes correctly only in case referencing between
  layers (IDs <- IDREFs) is correct
  
  @param lang
  @param layers
  @return text corpus data composed of the provided layers