a method to retrieve the ip of system running docker

        :return: string with ip address of system

def ip(self):

        '''
            a method to retrieve the ip of system running docker

        :return: string with ip address of system
        '''

        if self.localhost.os.sysname == 'Windows' and float(self.localhost.os.release) < 10:
            sys_cmd = 'docker-machine ip %s' % self.vbox
            system_ip = self.command(sys_cmd).replace('\n','')
        else:
            system_ip = self.localhost.ip

        return system_ip