Add example of the provided instance usage

examples/providers/provided_instance.py

@@ -0,0 +1,38 @@
+"""Example of the injecting of provided instance attributes and items."""
+
+from dependency_injector import providers
+
+
+class Service:
+    def __init__(self):
+        self.value = 'foo'
+        self.values = [self.value]
+
+    def get_value(self):
+        return self.value
+
+    def __getitem__(self, item):
+        return self.values[item]
+
+
+class Client:
+    def __init__(self, value1, value2, value3):
+        self.value1 = value1
+        self.value2 = value2
+        self.value3 = value3
+
+
+service = providers.Singleton(Service)
+
+client_factory = providers.Factory(
+    Client,
+    value1=service.provided.value,
+    value2=service.provided.values[0],
+    value3=service.provided.get_value.call(),
+)
+
+
+if __name__ == '__main__':
+    client = client_factory()
+
+    assert client.value1 == client.value2 == client.value3 == 'foo'