Get historical market data.
        Connects to Blotter and gets historical data from storage

        :Parameters:
            symbols : list
                List of symbols to fetch history for
            start : datetime / string
                History time period start date
                datetime or YYYY-MM-DD[ HH:MM[:SS]] string)

        :Optional:
            end : datetime / string
                History time period end date
                (datetime or YYYY-MM-DD[ HH:MM[:SS]] string)
            resolution : string
                History resoluton (Pandas resample, defaults to 1T/1min)
            tz : string
                History timezone (defaults to UTC)

        :Returns:
            history : pd.DataFrame
                Pandas DataFrame object with historical data for all symbols

def get_history(self, symbols, start, end=None, resolution="1T", tz="UTC"):
        """Get historical market data.
        Connects to Blotter and gets historical data from storage

        :Parameters:
            symbols : list
                List of symbols to fetch history for
            start : datetime / string
                History time period start date
                datetime or YYYY-MM-DD[ HH:MM[:SS]] string)

        :Optional:
            end : datetime / string
                History time period end date
                (datetime or YYYY-MM-DD[ HH:MM[:SS]] string)
            resolution : string
                History resoluton (Pandas resample, defaults to 1T/1min)
            tz : string
                History timezone (defaults to UTC)

        :Returns:
            history : pd.DataFrame
                Pandas DataFrame object with historical data for all symbols
        """
        return self.blotter.history(symbols, start, end, resolution, tz)