Method valid

Libs/sol/sol.hpp:23209–23214

		}

		bool valid() const {
			auto pp = stack::push_pop(tbl);
			auto p = stack::probe_get_field<std::is_same<meta::unqualified_t<Table>, global_table>::value>(lua_state(), key, lua_gettop(lua_state()));
			lua_pop(lua_state(), p.levels);
			return p;
		}

		int push() const noexcept {
			return push(this->lua_state());