code: def _store_dicom_paths(self, folders):
          
          if isinstance(folders, str):
              folders = [folders]
  
          for folder in folders:
  
              if not os.path.exists(folder):
                  raise FolderNotFound(folder)
  
              self.items.extend(list(find_all_dicom_files(folder)))
docs: Search for dicoms in folders and save file paths into
          self.dicom_paths set.
  
          :param folders: str or list of str