code: def _update_cache(self):
          " If the original registry was changed. Update our copy version. "
          expected_version = (self.registry._version, self._extra_registry._version)
  
          if self._last_version != expected_version:
              registry2 = Registry()
  
              # Copy all bindings from `self.registry`, adding our condition.
              for reg in (self.registry, self._extra_registry):
                  for b in reg.key_bindings:
                      registry2.key_bindings.append(
                          _Binding(
                              keys=b.keys,
                              handler=b.handler,
                              filter=self.filter & b.filter,
                              eager=b.eager,
                              save_before=b.save_before))
  
              self._registry2 = registry2
              self._last_version = expected_versiof _update_cache(self):
          " If the original registry was changed. Update our copy version. "
          expected_version = (self.registry._version, self._extra_registry._version)
  
          if self._last_version != expected_version:
              registry2 = Registry()
  
              # Copy all bindings from `self.registry`, adding our condition.
              for reg in (self.registry, self._extra_registry):
                  for b in reg.key_bindings:
                      registry2.key_bindings.append(
                          _Binding(
                              keys=b.keys,
                              handler=b.handler,
                              filter=self.filter & b.filter,
                              eager=b.eager,
                              save_before=b.save_before))
  
              self._registry2 = registry2
              self._last_version = expected_version
docs: If the original registry was changed. Update our copy version.