code: def parse_extension_arg(arg, arg_dict):
      
  
      match = re.match(r'^(([^\d\W]\w*)(\.[^\d\W]\w*)*)=(.*)$', arg)
      if match is None:
          raise ValueError(
              "invalid extension argument '%s', must be in key=value form" % arg
          )
  
      name = match.group(1)
      value = match.group(4)
      arg_dict[name] = value
docs: Converts argument strings in key=value or key.namespace=value form
      to dictionary entries
  
      Parameters
      ----------
      arg : str
          The argument string to parse, which must be in key=value or
          key.namespace=value form.
      arg_dict : dict
          The dictionary into which the key/value pair will be added