Update docs about writing custom providers

docs/providers/custom.rst

@@ -5,27 +5,23 @@ List of *Dependency Injector* providers could be widened with custom providers.
 
 Below are some tips and recommendations that have to be met:
 
-    1. Every custom provider has to extend base provider class -
-       ``dependency_injector.providers.Provider``.
+    1. Every custom provider has to extend base provider class - 
+       ``di.Provider``.
     2. Cusom provider's ``__init__()`` could be overriden with only condition: 
-       parent initializer 
-       (``dependency_injector.providers.Provider.__init__()``) has to be called.
+       parent initializer (``di.Provider.__init__()``) has to be called.
     3. Providing strategy has to be implemented in custom provider's 
        ``_provide()`` method. All ``*args`` & ``**kwargs`` that will be
-       recieved by ``dependency_injector.providers.Provider.__call__()`` will be
-       transefed 
-       to custom provider's ``_provide()``. 
+       recieved by ``di.Provider.__call__()`` will be transefed to custom 
+       provider's ``_provide()``. 
     4. If custom provider is based on some standard providers, it is better to
        use delegation of standard providers, then extending of them.
     5. If custom provider defines any attributes, it is good to list them in 
        ``__slots__`` attribute (as *Dependency Injector* does). It can save 
        some memory.
-    6. If custom provider deals with injections (e.g. ``Factory``, 
-       ``Singleton`` providers), it is strongly recommended to use 
-       ``dependency_injector.injections.Injection`` and its subclasses:
-       ``dependency_injector.injections.KwArg``, 
-       ``dependency_injector.injections.Attribute`` and 
-       ``dependency_injector.injections.Method``. 
+    6. If custom provider deals with injections (e.g. ``di.Factory``, 
+       ``di.Singleton`` providers), it is strongly recommended to be 
+       consistent with ``di.Factory``, ``di.Singleton`` and ``di.Callable`` 
+       providers style. 
 
 Example:
 

examples/providers/custom_factory.py

@@ -1,7 +1,6 @@
-"""Custom `Factory` example."""
+"""Custom `di.Factory` example."""
 
-from dependency_injector.providers import Provider
-from dependency_injector.providers import Factory
+import dependency_injector as di
 
 
 class User(object):
@@ -9,7 +8,7 @@ class User(object):
     """Example class User."""
 
 
-class UsersFactory(Provider):
+class UsersFactory(di.Provider):
 
     """Example users factory."""
 
@@ -17,7 +16,7 @@ class UsersFactory(Provider):
 
     def __init__(self):
         """Initializer."""
-        self._factory = Factory(User)
+        self._factory = di.Factory(User)
         super(UsersFactory, self).__init__()
 
     def _provide(self, *args, **kwargs):