TElPGPSignersUserIDSignatureSubpacket is a descendant of TElPGPSignatureSubpacket class.
The following paragraph is taken from RFC 2440 - OpenPGP messages format, part 188.8.131.52.:
«This subpacket allows a keyholder to state which user id is responsible for the signing. Many keyholders use a single key for different purposes, such as business communications as well as personal communications. This subpacket allows such a keyholder to state which of their roles is making a signature. »