import ... the following python module to use openPMD-api:
Public facade import (serial and MPI)
As demonstrated in our python examples, MPI-parallel scripts must import
from mpi4py import MPI prior to importing
openpmd_api in order to initialize MPI first.
Otherwise, errors of the following kind will occur:
The MPI_Comm_test_inter() function was called before MPI_INIT was invoked. This is disallowed by the MPI standard. Your MPI job will now abort.