Update the image's state information by making a call to fetch
        the current image attributes from the service.

        :type validate: bool
        :param validate: By default, if EC2 returns no data about the
                         image the update method returns quietly.  If
                         the validate param is True, however, it will
                         raise a ValueError exception if no data is
                         returned from EC2.

def update(self, validate=False):
        """
        Update the image's state information by making a call to fetch
        the current image attributes from the service.

        :type validate: bool
        :param validate: By default, if EC2 returns no data about the
                         image the update method returns quietly.  If
                         the validate param is True, however, it will
                         raise a ValueError exception if no data is
                         returned from EC2.
        """
        rs = self.connection.get_all_images([self.id])
        if len(rs) > 0:
            img = rs[0]
            if img.id == self.id:
                self._update(img)
        elif validate:
            raise ValueError('%s is not a valid Image ID' % self.id)
        return self.state