code: def add_log_entry(self, process_name, timeperiod, msg):
          
          tree = self.get_tree(process_name)
          node = tree.get_node(process_name, timeperiod)
          node.add_log_entry([datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S'), msg])
docs: adds a non-persistent log entry to the tree node