Any value, including null or undefined.
Whether the value has a Decimal scalar and valid counted unit arrays. Invalid or unreadable properties return false. Inputs are never normalized in place.
Checks registered unit/prefix tokens, positive safe-integer powers, and duplicate-count overflow. NaN and Infinity are valid Decimal scalars. This does not check physical temperature restrictions; construct a Quantity for those. Decimal instances from the same installed package, including clones, are accepted; serialized numeric or string scalars must first be converted to Decimal.
Validate the scalar and counted unit records of a quantity definition.