def is_double_callable(application):
    """
    Tests to see if an application is a legacy-style (double-callable) application.
    """
    # Look for a hint on the object first
    if getattr(application, "_asgi_single_callable", False):
        return False
    if getattr(application, "_asgi_double_callable", False):
        return True
    # Uninstanted classes are double-callable
    if inspect.isclass(application):
        return True
    # Instanted classes depend on their __call__
    if hasattr(application, "__call__"):
        # We only check to see if its __call__ is a coroutine function -
        # if it's not, it still might be a coroutine function itself.
        if asyncio.iscoroutinefunction(application.__call__):
            return False
    # Non-classes we just check directly
    return not asyncio.iscoroutinefunction(application)

    Tests to see if an application is a legacy-style (double-callable) application.
    
src/asgiref/compatibility.py