old_contents: from corehq.warehouse.const import (
      GROUP_DIM_SLUG,
      GROUP_STAGING_SLUG,
      USER_DIM_SLUG,
      USER_GROUP_DIM_SLUG,
  )
  from corehq.warehouse.etl import CustomSQLETLMixin
  from corehq.warehouse.loaders.base import BaseLoader
  
  
  class UserGroupDimLoader(BaseLoader, CustomSQLETLMixin):
      """
      Dimension for User and Group mapping
  
      Grain: user_id, group_id
      """
      slug = USER_GROUP_DIM_SLUG
  
      @classmethod
      def dependencies(cls):
          return [USER_DIM_SLUG, GROUP_DIM_SLUG, GROUP_STAGING_SLUG]
  
new_contents: from corehq.warehouse.const import (
      GROUP_DIM_SLUG,
      GROUP_STAGING_SLUG,
      USER_DIM_SLUG,
      USER_GROUP_DIM_SLUG,
  )
  from corehq.warehouse.etl import CustomSQLETLMixin
  from corehq.warehouse.loaders.base import BaseLoader
  from corehq.warehouse.models import UserGroupDim
  
  
  class UserGroupDimLoader(BaseLoader, CustomSQLETLMixin):
      """
      Dimension for User and Group mapping
  
      Grain: user_id, group_id
      """
      slug = USER_GROUP_DIM_SLUG
      model_cls = UserGroupDim
  
      @classmethod
      def dependencies(cls):
          return [USER_DIM_SLUG, GROUP_DIM_SLUG, GROUP_STAGING_SLUG]
  
subject: add missing model_cls