chore: use alias & constants (#2785)

* chore: use alias and constants

* fix(rl): solve circular dependecy

* chore: nit right constant

* chore: pre-commit

* chore(script): conflict tokenizer train

---------

Signed-off-by: Steven Palma <imstevenpmwork@ieee.org>

src/lerobot/processor/tokenizer_processor.py

@@ -38,7 +38,7 @@ from lerobot.utils.constants import (
 )
 from lerobot.utils.import_utils import _transformers_available
 
-from .core import EnvTransition, TransitionKey
+from .core import EnvTransition, RobotObservation, TransitionKey
 from .pipeline import ActionProcessorStep, ObservationProcessorStep, ProcessorStepRegistry
 
 # Conditional import for type checking and lazy loading
@@ -139,7 +139,7 @@ class TokenizerProcessorStep(ObservationProcessorStep):
 
         return None
 
-    def observation(self, observation: dict[str, Any]) -> dict[str, Any]:
+    def observation(self, observation: RobotObservation) -> RobotObservation:
         """
         Tokenizes the task description and adds it to the observation dictionary.