filter unfinished examples and add timer to ensure upper limit of each example

demo.py

@@ -0,0 +1,16 @@
+import signal
+import time
+
+def handler(signo, frame):
+    raise RuntimeError("Timeout")
+
+signal.signal(signal.SIGALRM, handler)
+
+while True:
+    try:
+        signal.alarm(5) # seconds
+        time.sleep(10)
+        print("Working...")
+    except Exception as e :
+        print(e)
+        continue