<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_image_attribute(self, image_id, attribute='launchPermission'):
 """ Gets an attribute from an image. :type image_id: string :param image_id: The Amazon image id for which you want info about :type attribute: string :param attribute: The attribute you need information about. Valid choices are: * launchPermission * productCodes * blockDeviceMapping :rtype: :class:`boto.ec2.image.ImageAttribute` :return: An ImageAttribute object representing the value of the attribute requested """

        params = {'ImageId' : image_id,
                  'Attribute' : attribute}
        return self.get_object('DescribeImageAttribute', params,
                               ImageAttribute, verb='POST')