code: def _check_toolplus(x):
      
      import argparse
      Tool = collections.namedtuple("Tool", ["name", "fname"])
      std_choices = set(["data", "cadd", "dbnsfp", "ericscript"])
      if x in std_choices:
          return Tool(x, None)
      elif "=" in x and len(x.split("=")) == 2:
          name, fname = x.split("=")
          fname = os.path.normpath(os.path.realpath(fname))
          if not os.path.exists(fname):
              raise argparse.ArgumentTypeError("Unexpected --toolplus argument for %s. File does not exist: %s"
                                               % (name, fname))
          return Tool(name, fname)
      else:
          raise argparse.ArgumentTypeError("Unexpected --toolplus argument. Expect toolname=filename.")
docs: Parse options for adding non-standard/commercial tools like GATK and MuTecT.