Function call_meta 

pub fn call_meta(
    state: &mut LuaState,
    obj: i32,
    event: &[u8],
) -> Result<bool, LuaError>

Call the metafield event of obj with obj as argument, pushing one result. Returns true if the meta-method existed and was called.

C: LUALIB_API int luaL_callmeta(lua_State *L, int obj, const char *event)