code: def clear(cls, fn):
          # type: (FunctionType) -> None
          
          if hasattr(fn, cls.CACHE_VAR):
              delattr(fn, cls.CACHE_VAR)
docs: Clear result cache on the given function.
  
          If the function has no cached result, this call will do nothing.
  
          Args:
              fn (FunctionType):
                  The function whose cache should be cleared.