A reference to the entity this score is attached to. Discriminated by "kind" — one of trace, observation, session, or experiment.
Subject is a trace-level score.
Subject is an observation-level score scoped to a trace.
Subject is a session-level score.
Subject is a dataset run (experiment) score.
A reference to the entity this score is attached to. Discriminated by "kind" — one of trace, observation, session, or experiment.