PDFComponent
Fits continuous families to a group by delegating to KSL's continuous distribution modeler.
Failure is detected using KSL's own signal rather than a re-derived list of preconditions. Every parameter estimator returns an estimation result carrying a success flag and a diagnostic message, and the modeler's own scoring stage discards a result when either the flag is false or no parameters were produced. This class applies the same predicate, for two reasons: a hand-maintained list of conditions drifts from what the estimators actually check, and reimplementing a library idiom works against the goal of lifting this package into the library.
The test is a disjunction because an estimation result is explicitly permitted to report failure while still carrying parameters; checking only for the absence of parameters would admit a fit that the estimator itself disowns.
Parameters
the candidate families to fit, defaulting to the modeler's full catalog
whether the modeler may estimate a left shift for a group. A shift costs one additional estimated parameter, which is counted in the candidate.