def invoke(*args)
      task_args = TaskArguments.new(arg_names, args)
      invoke_with_call_chain(task_args, InvocationChain::EMPTY)
    end
def invoke(*args)
      task_args = TaskArguments.new(arg_names, args)
      invoke_with_call_chain(task_args, InvocationChain::EMPTY)
    end
Invoke the task if it is needed.  Prerequisites are invoked first.