code: def merge_trd_mkt_stock_str(trd_mkt, partial_stock_str):
      
      mkt_qot = Market.NONE
      mkt = TRADE.REV_TRD_MKT_MAP[trd_mkt] if trd_mkt in TRADE.REV_TRD_MKT_MAP else TrdMarket.NONE
      if mkt == TrdMarket.HK:
          mkt_qot = Market.HK
      elif mkt == TrdMarket.US:
          mkt_qot = Market.US
      elif mkt == TrdMarket.HKCC or mkt == TrdMarket.CN:
          if partial_stock_str.startswith('6') or partial_stock_str.startswith('9'):
              mkt_qot = Market.SH
          else:
              mkt_qot = Market.SZ
      else:
          raise Exception("merge_trd_mkt_stock_str: unknown trd_mkt.")
  
      return merge_qot_mkt_stock_str(MKT_MAP[mkt_qot], partial_stock_str)
docs: Merge the string of stocks
      :param market: market code
      :param partial_stock_str: original stock code string. i.e. "AAPL","00700", "000001"
      :return: unified representation of a stock code. i.e. "US.AAPL", "HK.00700", "SZ.000001"