/**
  * Get normalized parameters
  *
  * @return String - Normalized Parameters
  */
 private function getNormalizedParameters()
 {
     $params = $this->parameters;
     // Remove oauth_signature if present
     // Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
     if (isset($params['oauth_signature'])) {
         unset($params['oauth_signature']);
     }
     return OAuthUtils::buildHTTPQuery($params);
 }