_attachChangeAndDefaultFileEvent(form_id) {
        const elements = this._collection[form_id].getInputs();
        [].forEach.call(elements, (form_control) => {

            this.__attachSingleChangeEvent(form_id, form_control);
            this.__observeSingleValueChange(form_id, form_control);

            // set default file input value
            if (form_control.type === 'file' && form_control.hasAttribute('value')) {
                const url = form_control.getAttribute('value');
                if (url !== '') {
                    this.setFileFromUrl(form_id, form_control.name, url);
                }
            }
        });
    }
Update FormData when user changed input's value
or when value changed from script

Also init default value for File inputs

@param {string} form_id

@private