code: function TemporaryCredentials(params) {
      AWS.Credentials.call(this);
      this.loadMasterCredentials();
      this.expired = true;
  
      this.params = params || {};
      if (this.params.RoleArn) {
        this.params.RoleSessionName =
          this.params.RoleSessionName || 'temporary-credentials';
      }
      this.service = new AWS.STS({params: this.params});
    }
docs: Creates a new temporary credentials object.
  
  @note In order to create temporary credentials, you first need to have
  "master" credentials configured in {AWS.Config.credentials}. These
  master credentials are necessary to retrieve the temporary credentials,
  as well as refresh the credentials when they expire.
  @param params [map] a map of options that are passed to the
  {AWS.STS.assumeRole} or {AWS.STS.getSessionToken} operations.
  If a `RoleArn` parameter is passed in, credentials will be based on the
  IAM role.
  @example Creating a new credenials object for generic temporary credentials
  AWS.config.credentials = new AWS.TemporaryCredentials();
  @example Creating a new credentials object for an IAM role
  AWS.config.credentials = new AWS.TemporaryCredentials({
  RoleArn: 'arn:aws:iam::1234567890:role/TemporaryCredentials',
  });
  @see AWS.STS.assumeRole
  @see AWS.STS.getSessionToken