Aggregating a numeric array

Hello all. I am trying to process the Hail table from gnomAD v4. In the hail table, there is a row field called freq with this schema:

Row fields:
    'locus': locus<GRCh38> 
    'alleles': array<str> 
    'freq': array<struct {
        AC: int32, 
        AF: float64, 
        AN: int32, 
        homozygote_count: int64

I want to annotate a new row that aggregates the entire array of ht.freq.AC per row, I tried it with this method but it didn’t work:

ht = ht.annotate(freq_AC_sum=hl.agg.array_sum(ht.freq.AC))
ExpressionException: 'Table.annotate: field 'freq_AC_sum'' does not support aggregation

May I please get some advice on how I can do that? Thank you very much.