code: public static CmsXmlGroupContainer createDocument(CmsObject cms, Locale locale, String modelUri)
      throws CmsException {
  
          // create the XML content
          CmsXmlGroupContainer content = new CmsXmlGroupContainer(cms, locale, modelUri);
          // call prepare for use content handler and return the result
          return (CmsXmlGroupContainer)content.getHandler().prepareForUse(cms, content);
      }
docs: Create a new instance of an group container based on the given default content,
  that will have all language nodes of the default content and ensures the presence of the given locale.<p>
  
  The given encoding is used when marshalling the XML again later.<p>
  
  @param cms the current users OpenCms content
  @param locale the locale to generate the default content for
  @param modelUri the absolute path to the group container file acting as model
  
  @throws CmsException in case the model file is not found or not valid
  
  @return the created group container