LUA mod to add flags to a monster?

LUA class definitions lists values that can be adjusted and “set_flag” to change the value of existing flags. But I don’t see any function to add new flags (say add “KEENNOSE” to all zombies).

mtype = {
string_id = “mtype_id”,
attributes = {
agro = { type = “int”, writable = true },
armor_acid = { type = “int”, writable = true },
armor_bash = { type = “int”, writable = true },
armor_cut = { type = “int”, writable = true },
armor_fire = { type = “int”, writable = true },
armor_stab = { type = “int”, writable = true },
attack_cost = { type = “int”, writable = true },
color = { type = “nc_color”, writable = true },
death_drops = { type = “string”, writable = true },
def_chance = { type = “int”, writable = true },
difficulty = { type = “int”, writable = true },
hp = { type = “int”, writable = true },
id = { type = “mtype_id” },
luminance = { type = “float”, writable = true },
melee_dice = { type = “int”, writable = true },
melee_sides = { type = “int”, writable = true },
melee_skill = { type = “int”, writable = true },
morale = { type = “int”, writable = true },
phase = { type = “phase_id”, writable = true },
revert_to_itype = { type = “string”, writable = true },
size = { type = “m_size”, writable = true },
sk_dodge = { type = “int”, writable = true },
speed = { type = “int”, writable = true },
sym = { type = “string”, writable = true },
upgrade_group = { type = “mongroup_id”, writable = true },
upgrades = { type = “bool”, writable = true },
half_life = { type = “int”, writable = true },
upgrade_into = { type = “mtype_id”, writable = true },
vision_day = { type = “int”, writable = true },
vision_night = { type = “int”, writable = true },
},
functions = {
{ name = “bloodType”, rval = “field_id”, args = { } },
{ name = “get_meat_itype”, rval = “string”, args = { } },
{ name = “gibType”, rval = “field_id”, args = { } },
{ name = “has_flag”, rval = “bool”, args = { “string” } },
{ name = “made_of”, rval = “bool”, args = { “material_id” } },
{ name = “has_special_attack”, rval = “bool”, args = { “string” } },
{ name = “in_category”, rval = “bool”, args = { “string” } },
{ name = “in_species”, rval = “bool”, args = { “species_id” } },
{ name = “nname”, rval = “string”, args = { “int” } },
{ name = “nname”, rval = “string”, args = { } },
{ name = “same_species”, rval = “bool”, args = { “mtype” } },
{ name = “set_flag”, rval = nil, args = { “string”, “bool” } },
}
},

This would make it easier to customize enemies, which is the easiest way to change the challenge in the game.