def features(indel_class):
    """Manage feature names 

    Args:
        indel_class (str): "s" for single-nucleotide indels (1-nt indels)
                           "m" for multi-nucleotide indels (>1-nt indels)
    Returns:
        features (list): a list of feature names
    """
    assert indel_class == "s" or indel_class == "m"

    features_s = [
        "is_ins",
        "is_gc_ins",
        "is_gc_del",
        "is_at_ins",
        "is_at_del",
        "is_splice",
        "is_truncating",
        "is_nmd_insensitive",
        "gc",
        "local_gc",
        "lc",
        "local_lc",
        "strength",
        "local_strength",
        "repeat",
        "indel_complexity",
        "ref_count",
        "alt_count",
        "is_multiallelic",
        "is_near_boundary",
        "is_bidirectional",
        "is_uniq_mapped",
        "cds_length",
        "indel_location",
        "equivalence_exists",
        "ipg",
        "is_on_db",
    ]

    features_m = [
        "is_ins",
        "indel_size",
        "is_inframe",
        "is_truncating",
        "is_splice",
        "is_nmd_insensitive",
        "gc",
        "local_gc",
        "lc",
        "local_lc",
        "strength",
        "local_strength",
        "repeat",
        "dissimilarity",
        "indel_complexity",
        "ref_count",
        "alt_count",
        "is_multiallelic",
        "is_near_boundary",
        "is_bidirectional",
        "is_uniq_mapped",
        "cds_length",
        "indel_location",
        "is_in_cdd",
        "equivalence_exists",
        "ipg",
        "is_on_db",
    ]

    if indel_class == "s":
        return features_s
    elif indel_class == "m":
        return features_m
    else:
        return None