Man pages matching name mpi_attr_get in section 3:

MPI_Attr_get.3.en	debian 10 / lam-mpidoc
MPI_Attr_get.3.en	debian 10 / mpich-doc
MPI_Attr_get.3.en	debian 11 / lam-mpidoc
MPI_Attr_get.3.en	debian 12 / lam-mpidoc
MPI_Attr_get.3.en	debian 12 / mpich-doc