code: def mpicommand(self, *args, **kwargs):
          
          if self.mpiexec is None:
              raise NotImplementedError("Override mpiexec to enable the simple OpenMP launcher")
          # example implementation
          ncores = kwargs.pop('ncores', 8)
          return [self.mpiexec, '-n', str(ncores)]
docs: Return a list of the mpi command portion of the commandline.
  
          Only allows primitive mpi at the moment:
             *mpiexec* -n *ncores* *mdrun* *mdrun-args*
  
          (This is a primitive example for OpenMP. Override it for more
          complicated cases.)