docs: def option_parser():
      """Option Parser to give various options."""
      usage = '''
               $ ./crawler -d5 <url>
                  Here in this case it goes till depth of 5 and url is target URL to
                  start crawling.
              '''
      version = "2.0.0"
  
      parser = optparse.OptionParser(usage=usage, version=version)
  
      parser.add_option("-l", "--links", action="store_true",
                        default=False, dest="links", help="links for target url")
  
      parser.add_option("-d", "--depth", action="store", type="int",
                        default=30, dest="depth", help="Maximum depth traverse")
      opts, args = parser.parse_args()
  
      if len(args) < 1:
          parser.print_help()
          raise SystemExit(1)
  
      return opts, args