'Update the information about an image, optionally along with a file
handle or bytestream iterator for image bits. If the optional file
handle for updated image bits is supplied, the image may not have
already uploaded bits for the image.
:param context: The `nova.context.Context` object for the request
:param id_or_uri: A UUID identifier or an image URI to look up image
information for.
:param image_info: A dict of information about the image that is
passed to the image registry.
:param data: Optional file handle or bytestream iterator that is
passed to backend storage.
:param purge_props: Optional, defaults to False. If set, the backend
image registry will clear all image properties
and replace them the image properties supplied
in the image_info dictionary\'s \'properties\'
collection.'

def update(self, context, id_or_uri, image_info, data=None, purge_props=False):

    (session, image_id) = self._get_session_and_image_id(context, id_or_uri)
    return session.update(context, image_id, image_info, data=data, purge_props=purge_props)
