'Takes the CSV directory, the events queue and a possible
list of initial ticker symbols then creates an (optional)
list of ticker subscriptions and associated prices.'

def __init__(self, csv_dir, events_queue, init_tickers=None, start_date=None, end_date=None):

    self.csv_dir = csv_dir
    self.events_queue = events_queue
    self.continue_backtest = True
    self.tickers = {}
    self.tickers_data = {}
    if (init_tickers is not None):
        for ticker in init_tickers:
            self.subscribe_ticker(ticker)
    self.start_date = start_date
    self.end_date = end_date
    self.bar_stream = self._merge_sort_ticker_data()
