docs: def failed(self, group=None, start=0, limit=25):
          '''If no group is provided, this returns a JSON blob of the counts of
          the various types of failures known. If a type is provided, returns
          paginated job objects affected by that kind of failure.'''
          if not group:
              return json.loads(self.client('failed'))
          else:
              results = json.loads(
                  self.client('failed', group, start, limit))
              results['jobs'] = self.get(*results['jobs'])
              return results