docs: def find_slots(cls):
      """Return a set of all slots for a given class and its parents"""
  
      slots = set()
      for c in cls.__mro__:
          cslots = getattr(c, "__slots__", tuple())
  
          if not cslots:
              continue
          elif isinstance(cslots, (bstr, ustr)):
              cslots = (cslots,)
  
          slots.update(cslots)
  
      return slots