code: def _get_variants(data):
      
      active_vs = []
      if "variants" in data:
          variants = data["variants"]
          # CWL based list of variants
          if isinstance(variants, dict) and "samples" in variants:
              variants = variants["samples"]
          for v in variants:
              # CWL -- a single variant file
              if isinstance(v, six.string_types) and os.path.exists(v):
                  active_vs.append(_add_filename_details(v))
              elif (isinstance(v, (list, tuple)) and len(v) > 0 and
                    isinstance(v[0], six.string_types) and os.path.exists(v[0])):
                  for subv in v:
                      active_vs.append(_add_filename_details(subv))
              elif isinstance(v, dict):
                  if v.get("vrn_file"):
                      active_vs.append(v)
                  elif v.get("population"):
                      vrnfile = v.get("population").get("vcf")
                      active_vs.append(_add_filename_details(vrnfile))
                  elif v.get("vcf"):
                      active_vs.append(_add_filename_details(v.get("vcf")))
      return active_vs
docs: Retrieve variants from CWL and standard inputs for organizing variants.