Fix symmetry configuration (#126)

Fixes two issues:

-If symmetry is used, checks if function is callable (not only if data_augmentation is used)
-Raises an error if symmetry is used with recurrent actor critics.

Author: ClemensSchwarke

rsl_rl/algorithms/ppo.py

@@ -83,11 +83,14 @@ def __init__(
             if isinstance(symmetry_cfg["data_augmentation_func"], str):
                 symmetry_cfg["data_augmentation_func"] = string_to_callable(symmetry_cfg["data_augmentation_func"])
             # Check valid configuration
-            if symmetry_cfg["use_data_augmentation"] and not callable(symmetry_cfg["data_augmentation_func"]):
+            if not callable(symmetry_cfg["data_augmentation_func"]):
                 raise ValueError(
-                    "Data augmentation enabled but the function is not callable:"
-                    f" {symmetry_cfg['data_augmentation_func']}"
+                    f"Symmetry configuration exists but the function is not callable: "
+                    f"{symmetry_cfg['data_augmentation_func']}"
                 )
+            # Check if the policy is compatible with symmetry
+            if isinstance(policy, ActorCriticRecurrent):
+                raise ValueError("Symmetry augmentation is not supported for recurrent policies.")
             # Store symmetry configuration
             self.symmetry = symmetry_cfg
         else: