code: public synchronized Morphia map(final Set<Class> entityClasses) {
          if (entityClasses != null && !entityClasses.isEmpty()) {
              for (final Class entityClass : entityClasses) {
                  if (!mapper.isMapped(entityClass)) {
                      mapper.addMappedClass(entityClass);
                  }
              }
          }
          return this;
      }
docs: Maps a set of classes
  
  @param entityClasses the classes to map
  @return this