def split_procs(procs, valid_frac = .2):
    """Split the procedures into a
    training and validation set based
    on start time
    """
    procs.sort(key = lambda x: x.get_start_time())
    split_ind = int((1-valid_frac) *len(procs))
    training = procs[:split_ind]
    validation = procs[split_ind:]
    return (training, validation)