code: def _add_freq_options(config, opts, var2vcf_opts):
      
      if "-f" not in opts:
          freq = float(utils.get_in(config, ("algorithm", "min_allele_fraction"), 10)) / 100.0
          opts.extend(["-f", str(freq)])
          if "-f" not in var2vcf_opts:
              var2vcf_opts.extend(["-f", str(freq)])
docs: Setting -f option for vardict and var2vcf_valid
          Prioritizing settings in resources/vardict/options, then algorithm/min_allele_fraction:
      min_allele_fraction   "-f" in opts  var2vcfopts   ->   vardict -f            var2vcf -f
      yes                           yes   yes                opts                  var2vcfopts
      yes                           yes   -                  opts                  -
      yes                           -     yes                min_allele_fraction   var2vcfopts
      yes                           -     -                  min_allele_fraction   min_allele_fraction
      default                       yes   yes                opts                  var2vcfopts
      default                       yes   -                  opts                  -
      default                       -     yes                min_allele_fraction   var2vcfopts
      default                       -     -                  min_allele_fraction   min_allele_fraction