code: def market_order(
      side: "TradeSide",
      exchange_pair: "ExchangePair",
      price: float,
      size: float,
      portfolio: "Portfolio",
  ) -> "Order":
      """Creates a market order.
  
      Parameters
      ----------
      side : `TradeSide`
          The side of the order.
      exchange_pair : `ExchangePair`
          The exchange pair to perform the order for.
      price : float
          The current price.
      size : float
          The size of the order.
      portfolio : `Portfolio`
          The portfolio being used in the order.
  
      Returns
      -------
      `Order`
          A market order.
      """
  
      instrument = side.instrument(exchange_pair.pair)
      order = Order(
          step=portfolio.clock.step,
          side=side,
          trade_type=TradeType.MARKET,
          exchange_pair=exchange_pair,
          price=price,
          quantity=(size * instrument),
          portfolio=portfolio,
      )
  
      return order
  
file_path: tensortrade/tensortrade/oms/orders/create.py
imports: from tensortrade.oms.instruments import ExchangePair
  from tensortrade.oms.wallets import Portfolio
  from tensortrade.oms.orders import Order, OrderSpec, TradeSide, TradeType
  from tensortrade.oms.orders.criteria import Stop, Limit
label_desc: Use image node_id 1 for calling a global function with example usage: market_order(side, exchange_pair, price, size, portfolio) and returns: order