code: def const_return(func):
      
      result = _undef
  
      def ret_call(*args, **kwargs):
          nonlocal result
          if result is _undef:
              result = func(*args, **kwargs)
          return result
  
      return ret_call
docs: >>> from Redy.Magic.Classic import const_return
      >>> @const_return
      >>> def f(x):
      >>>     return x
      >>> r1 = f(1)
      >>> assert r1 is 1 and r1 is f(2)