data-models

Python types for chronological data streams: instances carry payload data plus BaseMetadata (timestamp, index).

Design pattern

• BaseMetadata — Minimal identity for one sample in a stream.
• BaseInstance — Payload + metadata; concrete types live under data_models.impl (e.g. ImageInstance, pose/TF types).

Downstream code should depend on these models rather than on ROS message classes directly. Pair with ros-python-conversions at the bag boundary.