```python:inference/core/workflows/core_steps/trackers/_base.py
from functools import lru_cache
from inference.core.workflows.execution_engine.entities.base import OutputDefinition
from inference.core.workflows.execution_engine.entities.types import OBJECT_DETECTION_PREDICTION_KIND
from typing import List

OUTPUT_KEY: str = "tracked_detections"


@lru_cache(maxsize=1)
def tracker_describe_outputs() -> List[OutputDefinition]:
    """Output definitions shared by all tracker blocks."""
    return [
        OutputDefinition(name=OUTPUT_KEY, kind=[OBJECT_DETECTION_PREDICTION_KIND]),
        OutputDefinition(name="new_instances", kind=[OBJECT_DETECTION_PREDICTION_KIND]),
        OutputDefinition(
            name="already_seen_instances",
            kind=[OBJECT_DETECTION_PREDICTION_KIND],
        ),
    ]
```