Group items into somatic calling batches (tumor-only or tumor/normal).

    Returns batches, where a data item may be in pairs, and somatic and non_somatic
    (which are the original list of items).

def somatic_batches(items):
    """Group items into somatic calling batches (tumor-only or tumor/normal).

    Returns batches, where a data item may be in pairs, and somatic and non_somatic
    (which are the original list of items).
    """
    non_somatic = []
    somatic = []
    data_by_batches = defaultdict(list)
    for data in items:
        if not get_paired_phenotype(data):
            non_somatic.append(data)
        else:
            somatic.append(data)
            batches = dd.get_batches(data)
            if batches:
                for batch in batches:
                    data_by_batches[batch].append(data)
    return data_by_batches.values(), somatic, non_somatic