final concurrency examples

futures/coroutine_purgatory.py

@@ -0,0 +1,14 @@
+@asyncio.coroutine
+def three_phases():
+    response1 = yield from fetch1(request1)
+    # phase 1
+    request2 = step1(response1)
+    response2 = yield from fetch2(request2)
+    # phase 2
+    request3 = step2(response2)
+    response3 = yield from fetch3(request3)
+    # phase 3
+    step3(response3)
+
+
+loop.create_task(three_phases)