I'm using gatk variantannotator to add some extra annotation to my vcf file, and got somehow unclear about the 'CountNs'. I've checked the doc https://gatk.broadinstitute.org/hc/en-us/articles/4404607611931-CountNs, but still could not think of a real world example. Does the N means any A,T,C,G? could you please provide a toy example?
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