lua_pop(L, 1);
lua_pushstring(L, "lat");
type = lua_gettable(L, -2);
lua_ensure(type == LUA_TSTRING || type == LUA_TNUMBER,
"Attribute 'lat' must be specified for backbone and must either be a string (in the right format; see docs) or a number.");
lua_pop(L, 1);
lua_pushstring(L, "lat");
type = lua_gettable(L, -2);
lua_ensure(type == LUA_TSTRING || type == LUA_TNUMBER,
"Attribute 'lat' must be specified for backbone and must either be a string (in the right format; see docs) or a number.");