Add joint calling information to variants, while collapsing independent regions.

def _combine_to_jointcaller(processed):
    """Add joint calling information to variants, while collapsing independent regions.
    """
    by_vrn_file = collections.OrderedDict()
    for data in (x[0] for x in processed):
        key = (tz.get_in(("config", "algorithm", "jointcaller"), data), data["vrn_file"])
        if key not in by_vrn_file:
            by_vrn_file[key] = []
        by_vrn_file[key].append(data)
    out = []
    for grouped_data in by_vrn_file.values():
        cur = grouped_data[0]
        out.append([cur])
    return out