triqs mpi environment

[daisychoco]

Hi,
I'm learning dft_tools through web tutorial page.
When I ran "import triqs.utility.mpi as mpi" I got

"Warning: could not identify MPI environment!
Starting serial run at: 2022-10-13 16:13:27.174887"

I am wondering how i can set MPI environment.
If I type "mpirun", I got
"mpirun could not find anything to do.
It is possible that you forgot to specify how many processes to run
via the "-np" argument." and I assumed mpi environment is already set.

Could you help to set triqs mpi enviorment ?

Regards,