DatasetSearchHit.num_pifs returns None

[enze-chen]

When return DatasetSearchHits using the SearchClient, the attribute num_pifs is not working properly. Instead of giving the number of PIFs in a dataset (intended), it appears to give None, always. Below is code that should reproduce the issue.

import os
from citrination_client import *

sc = CitrinationClient(os.environ['CITRINATION_API_KEY'], 'https://citrination.com').search
query = DatasetReturningQuery(
    size=100,
    query=DataQuery(
        system=PifSystemQuery(
            chemical_formula=ChemicalFieldQuery(
                filter=ChemicalFilter(
                    equal='As2S3')))))
res = sc.dataset_search(query)
print("The first dataset has {} PIFs.".format(res.hits[0].num_pifs))