code: def get_or_create_folder(self, folder_names):
          
          if not len(folder_names):
              return None
          current_parent = None
          for folder_name in folder_names:
              current_parent, created = Folder.objects.get_or_create(name=folder_name, parent=current_parent)
              if created:
                  self.folder_created += 1
                  if self.verbosity >= 2:
                      print("folder_created #%s folder : %s -- created : %s" % (self.folder_created, current_parent, created))
          return current_parent
docs: Gets or creates a Folder based the list of folder names in hierarchical
          order (like breadcrumbs).
  
          get_or_create_folder(['root', 'subfolder', 'subsub folder'])
  
          creates the folders with correct parent relations and returns the
          'subsub folder' instance.