Man pages matching name pmapi_internal in section 3:

PMAPI_INTERNAL.3.en	debian 10 / libpcp3-dev
pmapi_internal.3.en	debian 10 / libpcp3-dev
PMAPI_INTERNAL.3.en	debian 11 / libpcp3-dev
PMAPI_INTERNAL.3.en	debian 12 / libpcp3-dev