code: def unset_values(self):
          
          self._warn_for_no_prompt = False
          try:
              # set_value() already rejects undefined symbols, and they don't
              # need to be invalidated (because their value never changes), so we
              # can just iterate over defined symbols
              for sym in self.unique_defined_syms:
                  sym.unset_value()
  
              for choice in self.unique_choices:
                  choice.unset_value()
          finally:
              self._warn_for_no_prompt = True
docs: Resets the user values of all symbols, as if Kconfig.load_config() or
          Symbol.set_value() had never been called.