Add the PID to the resource usage reply

Author: echarles

ipykernel/kernelbase.py

@@ -929,7 +929,10 @@ def get_process_metric_value(self, process, name, attribute=None):
             return None
 
     async def usage_request(self, stream, ident, parent):
-        reply_content = {"hostname": socket.gethostname()}
+        reply_content = {
+            "hostname": socket.gethostname(),
+            "pid": os.getpid()
+        }
         current_process = psutil.Process()
         all_processes = [current_process] + current_process.children(recursive=True)
         process_metric_value = self.get_process_metric_value