@staticmethod
def find_chain(task_name, list_of_groups_of_chains):
    """find the chain containing the task
        :param `task_name` : The task to search for.
        :param `list_of_groups_of_chains` : list of groups of chains to search
            for the task

        :return : the list representing the chain containing task_name"""
    for group in list_of_groups_of_chains:
        for chain in group:
            if task_name in chain:
                return chain
    return None
