refine example doc and address https://github.com/deltachat/deltachat-core-rust/pull/1307#pullrequestreview-380876587

python/examples/echo_and_quit.py

@@ -1,11 +1,11 @@
 
 # content of echo_and_quit.py
 
-import deltachat
+from deltachat import account_hookimpl, run_cmdline
 
 
 class EchoPlugin:
-    @deltachat.hookspec.account_hookimpl
+    @account_hookimpl
     def process_incoming_message(self, message):
         print("process_incoming message", message)
         if message.text.strip() == "/quit":
@@ -17,13 +17,13 @@ class EchoPlugin:
             text = message.text
             message.chat.send_text("echoing from {}:\n{}".format(addr, text))
 
-    @deltachat.hookspec.account_hookimpl
+    @account_hookimpl
     def process_message_delivered(self, message):
         print("process_message_delivered", message)
 
 
 def main(argv=None):
-    deltachat.run_cmdline(argv=argv, account_plugins=[EchoPlugin()])
+    run_cmdline(argv=argv, account_plugins=[EchoPlugin()])
 
 
 if __name__ == "__main__":