/**
  * @param $form  array
  * @param $files File[] must be set with same keys as $form['worksheets'] array has
  * @return Import
  */
 public static function build($form, $files)
 {
     $import = new Import();
     if (isset($form['worksheets'])) {
         foreach ($form['worksheets'] as $worksheet_name => $worksheet) {
             if (isset($files[$worksheet_name])) {
                 $settings = Import_Settings_Builder::buildForm($worksheet);
                 $import->worksheets[$worksheet_name] = new Import_Worksheet($worksheet_name, $settings, $files[$worksheet_name]);
             }
         }
     }
     return $import;
 }