in src/session_credential.ts [10:20]
constructor(config: Config) {
const conf = new Config({
type: config.type,
accessKeyId: config.accessKeyId,
accessKeySecret: config.accessKeySecret,
securityToken: config.securityToken
});
super(conf);
this.sessionCredential = null;
this.durationSeconds = config.durationSeconds || 3600;
}