code: def find_checker(func: CallableT) -> Optional[CallableT]:
      
      contract_checker = None  # type: Optional[CallableT]
      for a_wrapper in _walk_decorator_stack(func):
          if hasattr(a_wrapper, "__preconditions__") or hasattr(a_wrapper, "__postconditions__"):
              contract_checker = a_wrapper
  
      return contract_checker
docs: Iterate through the decorator stack till we find the contract checker.