/**
  * Creates a new Microsoft_WindowsAzure_SharedAccessSignatureCredentials instance
  *
  * @param string $accountName Account name for Windows Azure
  * @param string $accountKey Account key for Windows Azure
  * @param boolean $usePathStyleUri Use path-style URI's
  * @param array $permissionSet Permission set
  */
 public function __construct($accountName = Microsoft_WindowsAzure_Credentials::DEVSTORE_ACCOUNT, $accountKey = Microsoft_WindowsAzure_Credentials::DEVSTORE_KEY, $usePathStyleUri = false, $permissionSet = array())
 {
     parent::__construct($accountName, $accountKey, $usePathStyleUri);
     $this->_permissionSet = $permissionSet;
 }