one more usecase

docs/source/usage.rst

@@ -57,6 +57,11 @@ Different ways to get/set a value:
             transaction.set_nowait('increment-4', value4 + 1)
             await transaction.commit()
 
+        with connection.transaction() as transaction:
+            value5 = transaction.get('increment-5', 0)
+            transaction.set_nowait('increment-5', value5 + 1)
+        await connection.commit()
+
 .. autoclass:: ptvp35.DbConnection
 
     .. automethod:: get