simplified step_backwards

gflownet/envs/tree.py

@@ -624,30 +624,18 @@ def step_backwards(
         Returns
         -------
         self.state : list
-            The sequence after executing the action
+            The state after executing the action.
 
         action : int
-            Action index
+            Given action.
 
         valid : bool
             False, if the action is not allowed for the current state.
         """
-        if self.continuous:
-            # Replace the continuous value of threshold by -1 to allow checking it.
-            action = self.action2representative(action)
-        do_step, self.state, action_to_check = self._pre_step(
-            action,
-            backward=True,
-            skip_mask_check=(skip_mask_check or self.skip_mask_check),
-        )
-        if not do_step:
-            return self.state, action, False
-        parents, parents_a = self.get_parents()
-        state_next = parents[parents_a.index(action)]
-        self.state = state_next
-        self.done = False
-        self.n_actions += 1
-        return self.state, action, True
+        # Replace the continuous value of threshold by -1 to allow checking it.
+        action_to_check = self.action2representative(action)
+        _, _, valid = super().step_backwards(action_to_check, skip_mask_check=skip_mask_check)
+        return self.state, action, valid
 
     def set_state(self, state: List, done: Optional[bool] = False):
         """