Return the data argument from a list of arguments
function(args) {
    if (args.length < 1 || !isPlainObject(args[0])) {
      return {};
    }

    if (!utils.isOptionsHash(args[0])) {
      return args.shift();
    }

    var argKeys = Object.keys(args[0]);

    var optionKeysInArgs = argKeys.filter(function(key) {
      return OPTIONS_KEYS.indexOf(key) > -1;
    });

    // In some cases options may be the provided as the first argument.
    // Here we're detecting a case where there are two distinct arguments
    // (the first being args and the second options) and with known
    // option keys in the first so that we can warn the user about it.
    if (optionKeysInArgs.length > 0 && optionKeysInArgs.length !== argKeys.length) {
      emitWarning(
        'Options found in arguments (' + optionKeysInArgs.join(', ') + '). Did you mean to pass an options ' +
        'object? See https://github.com/stripe/stripe-node/wiki/Passing-Options.'
      );
    }

    return {};
  }