old_contents: from django.contrib.admin.views.main import ChangeList
  
  class ListStyleAdminMixin(object):
      def get_row_css(self, obj, index):
          return ''
          
  
new_contents: 
  class ListStyleAdminMixin(object):
      def get_row_css(self, obj, index):
          return ''
  
subject: remove unused import