Deployer\Server\Configuration::setAuthenticationMethod PHP Method

    public function setAuthenticationMethod($authenticationMethod)
    {
        $this->authenticationMethod = $authenticationMethod;
        return $this;
    }

 /**
  * Using forward agent to authentication
  *
  * @return Builder
  */
 public function forwardAgent()
 {
     $this->config->setAuthenticationMethod(Configuration::AUTH_BY_AGENT);
     return $this;
 }