code: def get_theme(self):
          
          xblock_settings = self.get_xblock_settings(default={})
          if xblock_settings and self.theme_key in xblock_settings:
              return xblock_settings[self.theme_key]
          return self.default_theme_config
docs: Gets theme settings from settings service. Falls back to default (LMS) theme
          if settings service is not available, xblock theme settings are not set or does
          contain mentoring theme settings.