code: def _strelka_variant_stats(variant, sample_info):
      
      
      if variant.is_deletion or variant.is_insertion:
          # ref: https://sites.google.com/site/strelkasomaticvariantcaller/home/somatic-variant-output
          ref_depth = int(sample_info['TAR'][0]) # number of reads supporting ref allele (non-deletion)
          alt_depth = int(sample_info['TIR'][0]) # number of reads supporting alt allele (deletion)
          depth = ref_depth + alt_depth
      else:
          # Retrieve the Tier 1 counts from Strelka
          ref_depth = int(sample_info[variant.ref+"U"][0])
          alt_depth = int(sample_info[variant.alt+"U"][0])
          depth = alt_depth + ref_depth
      if depth > 0:
          vaf = float(alt_depth) / depth
      else:
          # unclear how to define vaf if no reads support variant
          # up to user to interpret this (hopefully filtered out in QC settings)
          vaf = None
  
      return VariantStats(depth=depth, alt_depth=alt_depth, variant_allele_frequency=vaf)
docs: Parse a single sample"s variant calling statistics based on Strelka VCF output
  
      Parameters
      ----------
      variant : varcode.Variant
      sample_info : dict
          Dictionary of Strelka-specific variant calling fields
  
      Returns
      -------
      VariantStats