text: #!/usr/bin/env python
  
  import asyncio
  import logging
  from typing import (
      List,
      Optional
  )
  from hummingbot.core.data_type.user_stream_tracker_data_source import UserStreamTrackerDataSource
  from hummingbot.logger import HummingbotLogger
  from hummingbot.core.data_type.user_stream_tracker import (
      UserStreamTrackerDataSourceType,
      UserStreamTracker
  )
  from hummingbot.core.utils.async_utils import (
      safe_ensure_future,
      safe_gather,
  )
  from hummingbot.market.liquid.liquid_api_user_stream_data_source import LiquidAPIUserStreamDataSource
  from hummingbot.market.liquid.liquid_auth import LiquidAuth
  
  
  class LiquidUserStreamTracker(UserStreamTracker):
      _bust_logger: Optional[HummingbotLogger] = None
  
      @classmethod
      def logger(cls) -> (HummingbotLogger):
          if cls._bust_logger is None:
              cls._bust_logger = logging.getLogger(__name__)
          return cls._bust_logger
  
      def __init__(self,
                   data_source_type: UserStreamTrackerDataSourceType = UserStreamTrackerDataSourceType.EXCHANGE_API,
                   liquid_auth: Optional[LiquidAuth] = None,
                   trading_pairs: Optional[List[str]] = []):
          super().__init__(data_source_type=data_source_type)
          self._liquid_auth: LiquidAuth = liquid_auth
          self._ev_loop: asyncio.events.AbstractEventLoop = asyncio.get_event_loop()
          self._trading_pairs = trading_pairs
          self._data_source: Optional[UserStreamTrackerDataSource] = None
          self._user_stream_tracking_task: Optional[asyncio.Task] = None
  
      @property
      def data_source(self) -> (UserStreamTrackerDataSource):
          if not self._data_source:
              if self._data_source_type is UserStreamTrackerDataSourceType.EXCHANGE_API:
                  self._data_source = LiquidAPIUserStreamDataSource(
                      liquid_auth=self._liquid_auth, trading_pairs=self._trading_pairs)
              else:
                  raise ValueError(f"data_source_type {self._data_source_type} is not supported.")
          return self._data_source
  
      @property
      def exchange_name(self) -> (str):
          return "liquid"
  
      async def start(self):
          self._user_stream_tracking_task = safe_ensure_future(
              self.data_source.listen_for_user_stream(self._ev_loop, self._user_stream)
          )
          await safe_gather(self._user_stream_tracking_task)
  