code: def get_vardict_command(data):
      
      vcaller = dd.get_variantcaller(data)
      if isinstance(vcaller, list):
          vardict = [x for x in vcaller if "vardict" in x]
          if not vardict:
              return None
          vardict = vardict[0]
      elif not vcaller:
          return None
      else:
          vardict = vcaller
      vardict = "vardict-java" if not vardict.endswith("-perl") else "vardict"
      return vardict
docs: convert variantcaller specification to proper vardict command, handling
      string or list specification