code: def test_mutex():
      mutex = Mutex(MPI.COMM_WORLD)
      mutex.lock()
      mutex.unlock()
      mutex.free()
  
file_path: mpi4py/demo/nxtval/nxtval-scalable.py
imports: from mpi4py import MPI
  import struct
label_desc: Use image node_id 2 for calling a global function with example usage: test_mutex() without return types