Hi, I am trying to filtering a vcf file by allele frequency. I'm using a file downloaded from the gnomad v2 liftover. I am using code as follows (python):

import vcf
vcf_reader = vcf.Reader(filename="gnomad.vcf.gz")
vcf_writer = vcf.Writer(open("filtered.vcf", "w"), vcf_reader)
for record in vcf_reader:
    if record.INFO['AF'][0] >= 0.5:
    vcf_writer.write_record(record)

And I have got error:

KeyError: 'AF'

But in column "INFO" in vcf has to be allele frequency. Any other ideas how to filter gnomad file by AF? Thanks in advance