def getAssociation(self, server_url, handle=None):
"""
This method returns an C{L{Association <openid.association.Association>}}
object from storage that matches the server URL and, if specified, handle.
It returns C{None} if no such association is found or if the matching
association is expired.
If no handle is specified, the store may return any association which
matches the server URL. If multiple associations are valid, the
recommended return value for this method is the one that will remain valid
for the longest duration.
"""
query = Association.all().filter('url', server_url)
if handle:
query.filter('handle', handle)
results = query.fetch(1)
if results:
association = OpenIDAssociation.deserialize(results[0].association)
if association.getExpiresIn() > 0:
# hasn't expired yet
return association
return None
