TRACE_STACK = [lambda f, *args, **kwargs: f(*args, **kwargs)]

@contextmanager
def trace(tracer):
  TRACE_STACK.append(tracer)
  yield
  TRACE_STACK.pop()

def traceable(func):
  def func_wrapped(*args, **kwargs):
    return TRACE_STACK[-1](func, *args, **kwargs)
  return func_wrapped