Man pages matching name mpi_type_set_attr in section 3:

MPI_Type_set_attr.3.en	debian 10 / lam4-dev
MPI_Type_set_attr.3.en	debian 10 / mpich-doc
MPI_Type_set_attr.3.en	debian 11 / lam4-dev
MPI_Type_set_attr.3.en	debian 12 / lam4-dev
MPI_Type_set_attr.3.en	debian 12 / mpich-doc