code: def _setup_call_false(vrn_file, rm_bed, base_dir, data, call_type):
      
      out_file = os.path.join(base_dir, "%s.vcf.gz" % call_type)
      if not utils.file_exists(out_file):
          with file_transaction(data, out_file) as tx_out_file:
              if not vrn_file.endswith(".gz"):
                  vrn_file = vcfutils.bgzip_and_index(vrn_file, out_dir=os.path.dirname(tx_out_file))
              cmd = ("bcftools view -R {rm_bed} -f 'PASS,.' {vrn_file} -O z -o {tx_out_file}")
              do.run(cmd.format(**locals()), "Prepare %s with empty reference" % call_type, data)
      return {call_type: out_file}
docs: Create set of false positives or ngatives for inputs with empty truth sets.