I am trying to fetch variant details, including population allele frequency (af), from the gnomAD database using the GraphQL API. However, the query does not return allele frequency for populations. When I add af under populations, I get the following error:

GraphQLError: Cannot query field 'af' on type 'VariantPopulation'. Did you mean 'ac' or 'an'?

GraphQL request:10:9
 9 |         populations {
10 |         af
   |         ^
11 |         id

My Query:

from gql import gql, Client
from gql.transport.aiohttp import AIOHTTPTransport

# GraphQL query to fetch variant details
query = gql(
"""
query VariantsInGene {
    gene(gene_symbol: "PTH", reference_genome: GRCh38) {
        variants(dataset: gnomad_r4) {
            variant_id
            pos
            exome {
                af
                populations {
                    id
                }
            }
        }
    }
}
"""
)

res = await client.execute_async(query)

• Fetching allele frequency (af) at the exome level (works fine).
• Adding af inside populations (causes the error).
• Checking available fields for VariantPopulation (suggests ac and an, but not af).

How can I retrieve allele frequency (af) per population in gnomAD GraphQL?

If I remove af from query it executes and generate output but no af is retrieved for populations: