func used as a function was not defined. Why?

Question

def add(x, y):
return x + y

def do_twice(func, x, y):
return func(func(x, y), func(x, y))

a = 5
b = 10

print(do_twice(add, a, b))

Answer 1

in the code playground the result is 30 without an error. there's no point to define func, it can be any function

Answer 2

thought as much