Man pages matching name mtext_get_prop_keys in section 3m17n:

mtext_get_prop_keys.3m17n.en	debian 10 / m17n-docs
mtext_get_prop_keys.3m17n.en	debian 11 / m17n-docs
mtext_get_prop_keys.3m17n.en	debian 12 / m17n-docs