code: def mpi_sum(x):
      return mpi_op(x, MPI.SUM)
  
file_path: spinningup/spinup/utils/mpi_tools.py
imports: from mpi4py import MPI
  import os, subprocess, sys
  import numpy
label_desc: Use image node_id 8 for calling a global function with example usage: mpi_sum(x) and returns: mpi_op