Changes:

	- implement the TestTask.overhead property that returns a float value representing non-group time.

mozci/task.py

@@ -2,13 +2,15 @@
 import json
 import os
 from abc import ABC, abstractmethod
+from argparse import Namespace
 from dataclasses import dataclass, field
 from enum import Enum
 from inspect import signature
 from statistics import median
 from typing import Dict, List, Optional
 
 import requests
+from adr.query import run_query
 from adr.util import memoized_property
 from loguru import logger
 from urllib3.response import HTTPResponse
@@ -358,6 +360,21 @@ def configuration(self):
         parts = config.split("-")
         return "-".join(parts[:-1] if parts[-1].isdigit() else parts)
 
+    @property
+    def overhead(self):
+        """Calculate the overhead of a task.
+
+        The methodology is simple: each task is associated with a duration value.
+        Obtain and sum the runtime of all groups in the task, then take the
+        difference and we have the overhead value.
+
+        Returns:
+            float: Difference of task duration and sum of group durations.
+        """
+        data = run_query("group_durations", Namespace(task_id=self.id))["data"]
+        group_runtime = [runtime for *_, runtime in data]
+        return self.duration - sum(group_runtime)
+
 
 # Don't perform type checking because of https://github.com/python/mypy/issues/5374.
 @dataclass  # type: ignore