Transfers an already answered call to another destination / phone number.
        Argument: to is a string
        Argument: **options is a set of optional keyword arguments.
        See https://www.tropo.com/docs/webapi/transfer

def transfer(self, to, **options):
        """
        Transfers an already answered call to another destination / phone number.
        Argument: to is a string
        Argument: **options is a set of optional keyword arguments.
        See https://www.tropo.com/docs/webapi/transfer
        """
        self._steps.append(Transfer(to, **options).obj)