Clean algorithm keys, handling items that can be specified as lists or single items.

def _clean_algorithm(data):
    """Clean algorithm keys, handling items that can be specified as lists or single items.
    """
    # convert single items to lists
    for key in ["variantcaller", "jointcaller", "svcaller"]:
        val = tz.get_in(["algorithm", key], data)
        if val:
            if not isinstance(val, (list, tuple)) and isinstance(val, six.string_types):
                val = [val]
            # check for cases like [false] or [None]
            if isinstance(val, (list, tuple)):
                if len(val) == 1 and not val[0] or (isinstance(val[0], six.string_types)
                                                    and val[0].lower() in ["none", "false"]):
                    val = False
            data["algorithm"][key] = val
    return data