def add_instruments(self, *instruments):
        """ add instruments after initialization """
        for instrument in instruments:
            if isinstance(instrument, ezibpy.utils.Contract):
                instrument = self.ibConn.contract_to_tuple(instrument)
                contractString = self.ibConn.contractString(instrument)
                self.instruments[contractString] = instrument
                self.ibConn.createContract(instrument)

        self.symbols = list(self.instruments.keys())
add instruments after initialization