code: def content_objs_from_labels(self, labels):
          '''[Label] -> [(content_id, FeatureCollection)]'''
          is_mapping = lambda obj: isinstance(obj, collections.Mapping)
          def is_valid_fc((cid, fc)):
              if fc is None:
                  return False
              if sum(1 for name in fc if is_mapping(fc[name])) == 0:
                  return False
              return True
  
          ids = set()
          for lab in labels:
              ids.add(lab.content_id1)
              ids.add(lab.content_id2)
          return list(ifilter(is_valid_fc, self.store.get_many(ids))f content_objs_from_labels(self, labels):
          '''[Label] -> [(content_id, FeatureCollection)]'''
          is_mapping = lambda obj: isinstance(obj, collections.Mapping)
          def is_valid_fc((cid, fc)):
              if fc is None:
                  return False
              if sum(1 for name in fc if is_mapping(fc[name])) == 0:
                  return False
              return True
  
          ids = set()
          for lab in labels:
              ids.add(lab.content_id1)
              ids.add(lab.content_id2)
          return list(ifilter(is_valid_fc, self.store.get_many(ids)))
docs: [Label] -> [(content_id, FeatureCollection)]