How to use the abcpy.backends.BackendMPI function in abcpy

'''
    If an exception is raised in a setUpModule then none of 
    the tests in the module will be run. 
    
    This is useful because the slaves run in a while loop on initialization
    only responding to the master's commands and will never execute anything else.

    On termination of master, the slaves call quit() that raises a SystemExit(). 
    Because of the behaviour of setUpModule, it will not run any unit tests
    for the slave and we now only need to write unit-tests from the master's 
    point of view. 
    '''
    global rank,backend_mpi
    comm = MPI.COMM_WORLD
    rank = comm.Get_rank()
    backend_mpi = BackendMPI()

'''
    If an exception is raised in a setUpModule then none of 
    the tests in the module will be run. 
    
    This is useful because the teams run in a while loop on initialization
    only responding to the scheduler's commands and will never execute anything else.

    On termination of scheduler, the teams call quit() that raises a SystemExit(). 
    Because of the behaviour of setUpModule, it will not run any unit tests
    for the team and we now only need to write unit-tests from the scheduler's 
    point of view. 
    '''
    global rank,backend_mpi
    comm = MPI.COMM_WORLD
    rank = comm.Get_rank()
    backend_mpi = BackendMPI(process_per_model=2)

def setup_backend():
    global backend

    from abcpy.backends import BackendMPI as Backend
    backend = Backend(process_per_model=2)

def setup_backend():
    global backend
    
    from abcpy.backends import BackendMPI as Backend
    backend = Backend()
    # The above line is equivalent to:

def setup_backend():
    global backend
    
    from abcpy.backends import BackendMPI as Backend
    backend = Backend(process_per_model=2)
    #backend = Backend()

def setup_backend(process_per_model):
    global backend
    from abcpy.backends import BackendMPI as Backend
    backend = Backend(process_per_model=process_per_model)

def setup_backend():
    global backend
    
    from abcpy.backends import BackendMPI as Backend
    backend = Backend(process_per_model=2)