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

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')