def METHOD_NAME(merged_datasets,num_evts_per_dataset):
    """ Return number of events per merged dataset
    Returns a dict `<merged_dataset>:<num_evts>'; see comments to function
    `merge_datasets' for an explanation of <merged_dataset>.
    """
    num_evts_per_merged_dataset = {}
    for merged_dataset,datasets in merged_datasets.items():
        num_evts = 0
        for dataset in datasets:
            num_evts = num_evts + num_evts_per_dataset[dataset]
        num_evts_per_merged_dataset[merged_dataset] = num_evts
    return num_evts_per_merged_dataset