def __init__(self, filename):
"""Raises IOError for invalid file types.
This MUST be the case in order to avoid the @memoize cache getting
filled up with invalid Photograph instances.
"""
Coordinates.__init__(self)
self.thumb = fetch_thumbnail(filename)
self.filename = filename
self.connect('notify::geoname', self.update_liststore_summary)
self.connect('notify::positioned', Widgets.button_sensitivity)
