docs: def refresh(self, credentials=False):
          """
          ::
          
              GET /:login/machines/:id
          
          :param credentials: whether to return machine passwords
          :type credentials: :py:class:`bool`
          
          Fetch the existing state and values for the 
          :py:class:`smartdc.machine.Machine` from the datacenter and commit the 
          values locally.
          """
          data = self.datacenter.raw_machine_data(self.id, 
                  credentials=credentials)
          self._save(data)