docs: def set_(self, state):
      """Set new state for machine."""
      if not self.can_be_(state):
          state = self._meta['translator'].translate(state)
          raise TransitionError(
              "Cannot transit from '{actual_value}' to '{value}'."
              .format(actual_value=self.actual_state.value, value=state.value)
          )
  
      self.force_set(state)