Retrieve loss of function plugin parameters for LOFTEE.
    https://github.com/konradjk/loftee

def _get_loftee(data):
    """Retrieve loss of function plugin parameters for LOFTEE.
    https://github.com/konradjk/loftee
    """
    ancestral_file = tz.get_in(("genome_resources", "variation", "ancestral"), data)
    if not ancestral_file or not os.path.exists(ancestral_file):
        ancestral_file = "false"
    vep = config_utils.get_program("vep", data["config"])
    args = ["--plugin", "LoF,human_ancestor_fa:%s,loftee_path:%s" %
            (ancestral_file, os.path.dirname(os.path.realpath(vep)))]
    return args