OptionalHoldoutThe model's Lineage JSON. Its evaluation record says whether Metrics were measured out of sample and whether
the verdict is withheld (a declared time index not evaluated as a forecast). MJMLModelEntity satisfies this.
Required (pass null when there is none) so a call site that drops it, and with it the withheld cap, fails to compile.
OptionalMetricsOptionalProblem
The minimal model slice the verdict needs — satisfied structurally by
MJMLModelEntityand the UI row.