code: def get_app_submodules(module_name):
      
      for name, module in get_app_modules():
          if module_has_submodule(module, module_name):
              yield name, import_module('{0}.{1}'.format(name, module_name))
docs: Get a specific sub module of the app
      :param module_name: module name to get
      :return: name, module tuple