docs: def get_variables(self, *args, **kwargs):
      """Provide a warning that get_variables on Sequential always returns ()."""
      tf.logging.warning(
          "Calling Sequential.get_variables, which will always return an empty "
          "tuple. get_variables() can only return variables created directly by "
          "a Module, or created by submodules directly created inside the "
          "Module. Sequential is constructed from already constructed submodules "
          "and so this will always be empty. See the documentation for more "
          "details, but tl;dr if you need to connect some modules sequentially "
          "and call get_variables on the result, writing a simple custom module "
          "is the simplest way. Another option is to call get_all_variables().")
      return super(Sequential, self).get_variables(*args, **kwargs)