feat(teleoperation): introduce HasTeleopEvents protocol and enhance teleop event handling (#1866)

- Added the HasTeleopEvents protocol to define a standard for teleoperators that provide control events.
- Implemented a runtime check to ensure teleoperators implement the get_teleop_events() method.
- Updated AddTeleopEventsAsInfoStep to utilize the new protocol, enhancing compatibility with custom teleoperators.
- Improved documentation for clarity on teleoperation event extraction and compatibility with built-in teleoperators.

src/lerobot/processor/hil_processor.py

@@ -1,7 +1,7 @@
 import math
 import time
 from dataclasses import dataclass
-from typing import Any
+from typing import Any, Protocol, TypeVar, runtime_checkable
 
 import numpy as np
 import torch
@@ -27,6 +27,40 @@ DISCRETE_PENALTY_KEY = "discrete_penalty"
 TELEOP_ACTION_KEY = "teleop_action"
 
 
+@runtime_checkable
+class HasTeleopEvents(Protocol):
+    """Minimal protocol for objects that provide teleoperation events.
+
+    This protocol only defines the additional get_teleop_events() method,
+    avoiding duplication of the entire Teleoperator interface.
+    """
+
+    def get_teleop_events(self) -> dict[str, Any]:
+        """Get extra control events from the teleoperator.
+
+        Returns:
+            Dictionary containing control events such as:
+                - is_intervention: bool - Whether human is currently intervening
+                - terminate_episode: bool - Whether to terminate the current episode
+                - success: bool - Whether the episode was successful
+                - rerecord_episode: bool - Whether to rerecord the episode
+        """
+        ...
+
+
+# Type variable constrained to Teleoperator subclasses that also implement events
+TeleopWithEvents = TypeVar("TeleopWithEvents", bound=Teleoperator)
+
+
+def _check_teleop_with_events(teleop: Teleoperator) -> None:
+    """Runtime check that a teleoperator implements get_teleop_events."""
+    if not isinstance(teleop, HasTeleopEvents):
+        raise TypeError(
+            f"Teleoperator {type(teleop).__name__} must implement get_teleop_events() method. "
+            f"Compatible teleoperators: GamepadTeleop, KeyboardEndEffectorTeleop"
+        )
+
+
 @ProcessorStepRegistry.register("add_teleop_action_as_complementary_data")
 @dataclass
 class AddTeleopActionAsComplimentaryDataStep(ComplementaryDataProcessorStep):
@@ -46,13 +80,29 @@ class AddTeleopActionAsComplimentaryDataStep(ComplementaryDataProcessorStep):
 @ProcessorStepRegistry.register("add_teleop_action_as_info")
 @dataclass
 class AddTeleopEventsAsInfoStep(InfoProcessorStep):
-    """Add teleoperator control events to transition info."""
+    """Add teleoperator control events to transition info.
 
-    teleop_device: Teleoperator
+    This processor step extracts control events from teleoperators that support
+    event-based interaction (intervention detection, episode termination, etc.).
+
+    Works with any teleoperator that inherits from Teleoperator and implements the
+    get_teleop_events() method, including custom user-defined teleoperators.
+
+    Built-in compatible teleoperators:
+        - GamepadTeleop: Uses gamepad buttons for control events
+        - KeyboardEndEffectorTeleop: Uses keyboard keys for control events
+    """
+
+    teleop_device: TeleopWithEvents
+
+    def __post_init__(self):
+        """Validate that the teleoperator supports events."""
+        _check_teleop_with_events(self.teleop_device)
 
     def info(self, info: dict) -> dict:
         new_info = dict(info)
-        teleop_events = getattr(self.teleop_device, "get_teleop_events", lambda: {})()
+
+        teleop_events = self.teleop_device.get_teleop_events()
         new_info.update(teleop_events)
         return new_info