code: def __iter__(self):
      yield self.bts_minute, BEFORE_TRADING_START_BAR
  
imports: import pandas
  from zipline.gens.sim_engine import BEFORE_TRADING_START_BAR
  from zipline.finance.asset_restrictions import NoRestrictions
  from zipline.finance import metrics
  from zipline.finance.trading import SimulationParameters
  from zipline.gens.tradesimulation import AlgorithmSimulator
  from zipline.testing.core import parameter_space
  import zipline.testing.fixtures
label_desc: Use image node_id 2 for calling the BeforeTradingStartsOnlyClock obj's underlying member method code with example usage: obj.__iter__() without return types