docs: def interval_to_milliseconds(interval):
      """Convert a Binance interval string to milliseconds
  
      :param interval: Binance interval string 1m, 3m, 5m, 15m, 30m, 1h, 2h, 4h, 6h, 8h, 12h, 1d, 3d, 1w
      :type interval: str
  
      :return:
           None if unit not one of m, h, d or w
           None if string not in correct format
           int value of interval in milliseconds
      """
      ms = None
      seconds_per_unit = {
          "m": 60,
          "h": 60 * 60,
          "d": 24 * 60 * 60,
          "w": 7 * 24 * 60 * 60
      }
  
      unit = interval[-1]
      if unit in seconds_per_unit:
          try:
              ms = int(interval[:-1]) * seconds_per_unit[unit] * 1000
          except ValueError:
              pass
      return ms