'Enable MFA Device for user.'

def enable_mfa_device(self, user_name, serial_number, authentication_code_1, authentication_code_2):

    user = self.get_user(user_name)
    if (serial_number in user.mfa_devices):
        raise IAMConflictException(u'EntityAlreadyExists', u'Device    {0}    already    exists'.format(serial_number))
    user.enable_mfa_device(serial_number, authentication_code_1, authentication_code_2)
