Add Selector provider example

examples/providers/selector.py

@@ -0,0 +1,28 @@
+"""`Selector` provider example."""
+
+from dependency_injector import providers
+
+
+class SomeClass:
+    ...
+
+
+class SomeOtherClass:
+    ...
+
+
+config = providers.Configuration()
+
+selector = providers.Selector(
+    config.one_or_another,
+    one=providers.Factory(SomeClass),
+    another=providers.Factory(SomeOtherClass),
+)
+
+config.override({'one_or_another': 'one'})
+some_instance_1 = selector()
+assert isinstance(some_instance_1, SomeClass)
+
+config.override({'one_or_another': 'another'})
+some_instance_2 = selector()
+assert isinstance(some_instance_2, SomeOtherClass)