message: Update backend.py
  "unique_object_name" methods' docstring example section typo is fixed, example section was using "_unique_layer_name" method name instead of "unique_object_name" method name
diff: @@ -933,8 +933,8 @@ def unique_object_name(name,
  Example:
  - _unique_layer_name('dense') # dense_1
  - _unique_layer_name('dense') # dense_2
  + unique_object_name('dense') # dense_1
  + unique_object_name('dense') # dense_2
  """
  if name_uid_map is None:
  