'Remove expired associations.
@return: tuple of (removed associations, remaining associations)'

def cleanup(self):

    remove = []
    for (handle, assoc) in self.assocs.iteritems():
        if (assoc.getExpiresIn() == 0):
            remove.append(handle)
    for handle in remove:
        del self.assocs[handle]
    return (len(remove), len(self.assocs))
