code: def unbind_handler(self, svc_ref):
          
          if svc_ref not in self._bound_references:
              # Unknown reference
              return False
  
          # Unregister its commands
          namespace, commands = self._reference_commands[svc_ref]
          for command in commands:
              self.unregister(namespace, command)
  
          # Release the service
          self._context.unget_service(svc_ref)
          del self._bound_references[svc_ref]
          del self._reference_commands[svc_ref]
          return True
docs: Called if a command service is gone.
          Unregisters its commands.
  
          :param svc_ref: A reference to the unbound service
          :return: True if the commands have been unregistered