def lookup_group(self, group_name):
'''Retrieve a Group object with the specified name or None. The field
names starting with "group_" should set group level attributes. The
field names starting with "default_" should set field defaults for the
group schemas.'''
group_key = self.get_group_key(group_name)
group_dict = self.redis.hgetall(group_key)
if group_dict:
group = Group(group_name, group_dict)
group.current_schema = self.get_latest_schema_for_group(group_name)
return group
