code: def _get_variant_file(x, key, suffix="", sample=None, ignore_do_upload=False):
      
      out = []
      fname = utils.get_in(x, key)
      upload_key = list(key)
      upload_key[-1] = "do_upload"
      do_upload = tz.get_in(tuple(upload_key), x, True)
      if fname and (ignore_do_upload or do_upload):
          if fname.endswith(".vcf.gz"):
              out.append({"path": fname,
                          "type": "vcf.gz",
                          "ext": "%s%s" % (x["variantcaller"], suffix),
                          "variantcaller": x["variantcaller"]})
              if utils.file_exists(fname + ".tbi"):
                  out.append({"path": fname + ".tbi",
                              "type": "vcf.gz.tbi",
                              "index": True,
                              "ext": "%s%s" % (x["variantcaller"], suffix),
                              "variantcaller": x["variantcaller"]})
          elif fname.endswith((".vcf", ".bed", ".bedpe", ".bedgraph", ".cnr", ".cns", ".cnn", ".txt", ".tsv")):
              ftype = utils.splitext_plus(fname)[-1][1:]
              if ftype == "txt":
                  extended_ftype = fname.split("-")[-1]
                  if "/" not in extended_ftype:
                      ftype = extended_ftype
              out.append({"path": fname,
                          "type": ftype,
                          "ext": "%s%s" % (x["variantcaller"], suffix),
                          "variantcaller": x["variantcaller"]})
      if sample:
          out_sample = []
          for x in out:
              x["sample"] = sample
              out_sample.append(x)
          return out_sample
      else:
          return out
docs: Retrieve VCF file with the given key if it exists, handling bgzipped.