revision 1

lerobot/common/policies/act/modeling_act.py

@@ -65,12 +65,16 @@ class ActionChunkingTransformerPolicy(nn.Module):
         "ActionChunkingTransformerPolicy does not handle multiple observation steps."
     )
 
-    def __init__(self, cfg: ActionChunkingTransformerConfig):
+    def __init__(self, cfg: ActionChunkingTransformerConfig | None = None):
         """
-        TODO(alexander-soare): Add documentation for all parameters once we have model configs established.
+        Args:
+            cfg: Policy configuration class instance or None, in which case the default instantiation of the
+                 configuration class is used.
         """
         super().__init__()
-        if getattr(cfg, "n_obs_steps", 1) != 1:
+        if cfg is None:
+            cfg = ActionChunkingTransformerConfig()
+        if cfg.n_obs_steps != 1:
             raise ValueError(self._multiple_obs_steps_not_handled_msg)
         self.cfg = cfg