code: function init(form_id) {
          var form = document.forms[form_id];
          if (form === undefined) {
              throw new Error('Form with ID ' + form_id + ' not found in DOM!');
          }
          if (this._collection[form_id] !== undefined) {
              throw new Error('Form with ID ' + form_id + ' already initiated!');
          }
          this._collection[form_id] = new BunnyFormData(form);
          this._attachChangeAndDefaultFileEvent(form_id);
          this._attachRadioListChangeEvent(form_id);
          this._attachDOMChangeEvent(form_id);
      }
docs: /*
  init methods
   
  Init form
  Must be called after DOMContentLoaded (ready)
  
  @param {string} form_id
  
  @throws Error