UNKNOWN
Represents a version requirement not successfully parsed from the metadata.
The old metadata format (from Kotlin 1.3 and earlier) did not have enough information for correct parsing of version requirements in some cases, so a stub of this kind is inserted instead.
KmVersionRequirement with this kind always has KmVersionRequirementLevel.HIDDEN level, 256.256.256 KmVersionRequirement.version, and null KmVersionRequirement.errorCode and KmVersionRequirement.message.
Version requirements of this kind are being ignored by writers (i.e., are not written back).