code: def test_buy_market_order(self):
      self.__test_impl(broker.Order.Action.BUY)
  
imports: import unittest
  from .None import broker_backtesting_test
  from pyalgotrade import broker
  from pyalgotrade.broker import slippage
  from pyalgotrade.broker import backtesting
  from pyalgotrade import bar
label_desc: Use image node_id 3 for calling the VolumeShareSlippageTestCase obj's underlying member method code with example usage: obj.test_buy_market_order() without return types