Form for backend in instant cms?

Question

PHP

Sorry, the question may seem childish to someone, but I did not find the answer in the documentation.
How to initialize a form on the backend in instant cms? What should be the form class name and file name?
I have a structure like this:

• controllers
  
  • map
    
    • backend
      
      • forms
        
        • form_settings.php
          
        
        
      • actions
        • settings.php
      
      
    • . . .
      
  
  

Content of form_settings.php :

class formMapSettings extends cmsForm {

    public function init() { . . . }
}

In settings.php I try to get the form like this:
$form = $this->getForm('form_settings');
and like this (for experiment):
$form = $this->getForm('backend/form_settings');
But I get false .