Man pages matching name tsmimehdrfieldvaluestringset in section 3ts:

TSMimeHdrFieldValueStringSet.3ts.en	debian 10 / trafficserver-dev
TSMimeHdrFieldValueStringSet.3ts.en	debian 11 / trafficserver-dev
TSMimeHdrFieldValueStringSet.3ts.en	debian 12 / trafficserver-dev