import refrom datetime import datetime, timezone, timedeltadef to_timestamp(dt_str, tz_str):    dt = datetime.strptime(dt_str, '%Y-%m-%d %H:%M:%S')    _ = re.match(r'^UTC([+-]?\d{1,2}):(\d\d)$', tz_str)    tz_hours = int(_.group(1))    tz_minutes = int(_.group(2))    tz = timezone(timedelta(hours=tz_hours, minutes=tz_minutes))    dt1 = dt.replace(tzinfo=tz)    return dt1.timestamp()