companion object {
    /** Arbitrary code point that's 2 bytes in UTF-8 and valid in IdnaMappingTable.txt. */
    private const val UNICODE_2 = 0x1a5

    /** Arbitrary code point that's 3 bytes in UTF-8 and valid in IdnaMappingTable.txt. */
    private const val UNICODE_3 = 0x2202

    /** Arbitrary code point that's 4 bytes in UTF-8 and valid in IdnaMappingTable.txt. */
    private const val UNICODE_4 = 0x1d11e

    /**