chore: replace hard-coded obs values with constants throughout all the source code (#2037)

* chore: replace hard-coded OBS values with constants throughout all the source code

* chore(tests): replace hard-coded OBS values with constants throughout all the test code

src/lerobot/utils/constants.py

@@ -17,19 +17,21 @@ from pathlib import Path
 
 from huggingface_hub.constants import HF_HOME
 
-OBS_ENV_STATE = "observation.environment_state"
-OBS_STATE = "observation.state"
-OBS_IMAGE = "observation.image"
-OBS_IMAGES = "observation.images"
-OBS_LANGUAGE = "observation.language"
+OBS_STR = "observation"
+OBS_PREFIX = OBS_STR + "."
+OBS_ENV_STATE = OBS_STR + ".environment_state"
+OBS_STATE = OBS_STR + ".state"
+OBS_IMAGE = OBS_STR + ".image"
+OBS_IMAGES = OBS_IMAGE + "s"
+OBS_LANGUAGE = OBS_STR + ".language"
+OBS_LANGUAGE_TOKENS = OBS_LANGUAGE + ".tokens"
+OBS_LANGUAGE_ATTENTION_MASK = OBS_LANGUAGE + ".attention_mask"
+
 ACTION = "action"
 REWARD = "next.reward"
 TRUNCATED = "next.truncated"
 DONE = "next.done"
 
-OBS_LANGUAGE_TOKENS = OBS_LANGUAGE + ".tokens"
-OBS_LANGUAGE_ATTENTION_MASK = OBS_LANGUAGE + ".attention_mask"
-
 ROBOTS = "robots"
 ROBOT_TYPE = "robot_type"
 TELEOPERATORS = "teleoperators"

src/lerobot/utils/visualization_utils.py

@@ -19,6 +19,8 @@ from typing import Any
 import numpy as np
 import rerun as rr
 
+from .constants import OBS_PREFIX, OBS_STR
+
 
 def init_rerun(session_name: str = "lerobot_control_loop") -> None:
     """Initializes the Rerun SDK for visualizing the control loop."""
@@ -63,7 +65,7 @@ def log_rerun_data(
         for k, v in observation.items():
             if v is None:
                 continue
-            key = k if str(k).startswith("observation.") else f"observation.{k}"
+            key = k if str(k).startswith(OBS_PREFIX) else f"{OBS_STR}.{k}"
 
             if _is_scalar(v):
                 rr.log(key, rr.Scalar(float(v)))