Make sure we work without original gym installed

fancy_rl/utils.py

@@ -1,9 +1,3 @@
-try:
-    import gym
-    from gym.spaces import Discrete as GymDiscrete, MultiDiscrete as GymMultiDiscrete, MultiBinary as GymMultiBinary, Box as GymBox
-except ImportError:
-    gym = None
-
 import gymnasium
 from gymnasium.spaces import Discrete as GymnasiumDiscrete, MultiDiscrete as GymnasiumMultiDiscrete, MultiBinary as GymnasiumMultiBinary, Box as GymnasiumBox
 from torchrl.data.tensor_specs import (
@@ -11,16 +5,26 @@ from torchrl.data.tensor_specs import (
     BinaryDiscreteTensorSpec, BoundedTensorSpec, UnboundedContinuousTensorSpec
 )
 
+try:
+    import gym
+    from gym.spaces import Discrete as GymDiscrete, MultiDiscrete as GymMultiDiscrete, MultiBinary as GymMultiBinary, Box as GymBox
+    gym_available = True
+except ImportError:
+    gym_available = False
+
 def is_discrete_space(action_space):
     discrete_types = (
-        GymDiscrete, GymMultiDiscrete, GymMultiBinary,
         GymnasiumDiscrete, GymnasiumMultiDiscrete, GymnasiumMultiBinary,
         DiscreteTensorSpec, OneHotDiscreteTensorSpec, MultiDiscreteTensorSpec, BinaryDiscreteTensorSpec
     )
     continuous_types = (
-        GymBox, GymnasiumBox, BoundedTensorSpec, UnboundedContinuousTensorSpec
+        GymnasiumBox, BoundedTensorSpec, UnboundedContinuousTensorSpec
     )
     
+    if gym_available:
+        discrete_types += (GymDiscrete, GymMultiDiscrete, GymMultiBinary)
+        continuous_types += (GymBox,)
+    
     if isinstance(action_space, discrete_types):
         return True
     elif isinstance(action_space, continuous_types):
@@ -29,7 +33,7 @@ def is_discrete_space(action_space):
         raise ValueError(f"Unsupported action space type: {type(action_space)}")
 
 def get_space_shape(action_space):
-    if gym is not None:
+    if gym_available:
         discrete_types = (GymDiscrete, GymMultiDiscrete, GymMultiBinary)
         continuous_types = (GymBox,)
     else: