Provide a range of options for HLA type, with decreasing resolution.

def hla_choices(orig_hla, min_parts=2):
    """Provide a range of options for HLA type, with decreasing resolution.
    """
    yield orig_hla
    try:
        int(orig_hla[-1])
    except ValueError:
        yield orig_hla[:-1]
    hla_parts = orig_hla.split(":")
    for sub_i in range(len(hla_parts) - min_parts + 1):
        yield ":".join(hla_parts[:len(hla_parts) - sub_i])