The fields of a schema that declares a type. anyOf and oneOf are not
among them: they apply to every value, null included, so a nullable type
beside one cannot admit null. A schema that may be null lists a
{ type: 'null' } branch in its anyOf or oneOf instead.
The fields of a schema that declares a
type.anyOfandoneOfare not among them: they apply to every value,nullincluded, so a nullabletypebeside one cannot admitnull. A schema that may be null lists a{ type: 'null' }branch in itsanyOforoneOfinstead.