Improve pymongo instrumentation example (open-telemetry#3315)

Author: andremm

instrumentation/opentelemetry-instrumentation-pymongo/src/opentelemetry/instrumentation/pymongo/__init__.py

@@ -57,12 +57,15 @@
 
     def request_hook(span, event):
         # request hook logic
+        pass
 
     def response_hook(span, event):
         # response hook logic
+        pass
 
     def failed_hook(span, event):
         # failed hook logic
+        pass
 
     # Instrument pymongo with hooks
     PymongoInstrumentor().instrument(request_hook=request_hook, response_hook=response_hook, failed_hook=failed_hook)