code: def reqMktDepth(
              self, contract: Contract, numRows: int = 5,
              isSmartDepth: bool = False, mktDepthOptions=None) -> Ticker:
          
          reqId = self.client.getReqId()
          ticker = self.wrapper.startTicker(reqId, contract, 'mktDepth')
          self.client.reqMktDepth(
              reqId, contract, numRows, isSmartDepth, mktDepthOptions)
          return ticker
docs: Subscribe to market depth data (a.k.a. DOM, L2 or order book).
  
          https://interactivebrokers.github.io/tws-api/market_depth.html
  
          Args:
              contract: Contract of interest.
              numRows: Number of depth level on each side of the order book
                  (5 max).
              isSmartDepth: Consolidate the order book across exchanges.
              mktDepthOptions: Unknown.
  
          Returns:
              The Ticker that holds the market depth in ``ticker.domBids``
              and ``ticker.domAsks`` and the list of MktDepthData in
              ``ticker.domTicks``.