docs and fix

docs/code_snippets/dependency_injection_snippet2.py

@@ -0,0 +1,13 @@
+import sqlite3
+from sqlite3 import Connection
+from typing import Iterable
+
+from dishka import Provider, Scope, provide
+
+
+class ConnectionProvider(Provider):
+    @provide(scope=Scope.REQUEST)
+    def new_connection(self) -> Iterable[Connection]:
+        conn = sqlite3.connect(":memory:")
+        yield conn
+        conn.close()