Fix lane_filter_node bugs: None header handling, missing subscriber, and dead code removal

[Copilot]

Summary

This PR fixes several bugs in lane_filter_node.py that could cause runtime errors and prevent proper functionality of the lane filtering system.

Bugs Fixed

1. Initial publishEstimate with None header

The node was calling self.publishEstimate(self.last_update_header) during initialization when self.last_update_header was still None. This would cause issues when trying to assign the header to a LanePose message.

Fixed by: Removing the premature call on line 127

2. Missing episode_start subscriber

The docstring documented a ~episode_start subscriber and the callback handler cbEpisodeStart was implemented, but the actual subscriber was never created. This prevented the lane filter from being reset when episodes start.

Fixed by: Adding the missing subscriber:

self.sub_episode_start = rospy.Subscriber(
    "~episode_start", EpisodeStart, self.cbEpisodeStart, queue_size=1
)

3. None header in prediction step

In cbPredict(), the method was calling publishEstimate(self.last_update_header) which could still be None on the very first segment callback, since cbPredict() is called before self.last_update_header is updated.

Fixed by: Adding a guard check:

if self.last_update_header is not None:
    self.publishEstimate(self.last_update_header)

4. Dead code removal

The static method _seg_msg_to_custom_type (19 lines) was defined but never used anywhere in the codebase.

Fixed by: Removing the unused method

5. Unused import

The numpy module was imported but never referenced in the code.

Fixed by: Removing the unused import

Impact

• Prevents potential runtime errors from publishing messages with None headers
• Enables proper episode-based filter reset functionality
• Cleaner, more maintainable codebase with 15 fewer lines of code
• No changes to existing working functionality

Testing

• ✓ Python syntax validation passed
• ✓ AST parsing successful
• ✓ File compilation verified

Original prompt

Fix these bugs:

@lane_filter_node_issues.md

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