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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def check_and_update_action_task_group_id(parent_link, decision_link, rebuilt_definitions):
 """Update the ``ACTION_TASK_GROUP_ID`` of an action after verifying. Actions have varying ``ACTION_TASK_GROUP_ID`` behavior. Release Promotion action tasks set the ``ACTION_TASK_GROUP_ID`` to match the action ``taskId`` so the large set of release tasks have their own taskgroup. Non-relpro action tasks set the ``ACTION_TASK_GROUP_ID`` to match the decision ``taskId``, so tasks are more discoverable inside the original on-push taskgroup. This poses a json-e task definition problem, hence this function. This function first checks to make sure the ``ACTION_TASK_GROUP_ID`` is a member of ``{action_task_id, decision_task_id}``. Then it makes sure the ``ACTION_TASK_GROUP_ID`` in the ``rebuilt_definition`` is set to the ``parent_link.task``'s ``ACTION_TASK_GROUP_ID`` so the json-e comparison doesn't fail out. Ideally, we want to obsolete and remove this function. Args: parent_link (LinkOfTrust):
 the parent link to test. decision_link (LinkOfTrust):
 the decision link to test. rebuilt_definitions (dict):
 the rebuilt definitions to check and update. Raises: CoTError: on failure. """

    rebuilt_gid = rebuilt_definitions['tasks'][0]['payload']['env']['ACTION_TASK_GROUP_ID']
    runtime_gid = parent_link.task['payload']['env']['ACTION_TASK_GROUP_ID']
    acceptable_gids = {parent_link.task_id, decision_link.task_id}
    if rebuilt_gid not in acceptable_gids:
        raise CoTError("{} ACTION_TASK_GROUP_ID {} not in {}!".format(
            parent_link.name, rebuilt_gid, acceptable_gids
        ))
    if runtime_gid != rebuilt_gid:
        log.debug("runtime gid {} rebuilt gid {}".format(runtime_gid, rebuilt_gid))
    rebuilt_definitions['tasks'][0]['payload']['env']['ACTION_TASK_GROUP_ID'] = runtime_gid