Example:

class O:
  "doc"
  a: int
  b = 2
  c: int = 1
  def f(self): return self.b
assert O().f() == 2

class O1(O):
  a1 = -1
  def f(self): return self.a1
assert O1().a == 0
assert O(O1()).f() == -1

# will error: class OO(O1, O): aaa = 1

class C:
  def f(self, b: float) -> int: return 1+int(b)
assert C().f(2) == 3

class CC(C):
  def f(self, b: float):
    return super().f(b)
assert CC().f(2) == 3