code: def check_fieldsets(*args, **kwargs):
      
      if hasattr(settings, "CONFIG_FIELDSETS") and settings.CONFIG_FIELDSETS:
          inconsistent_fieldnames = get_inconsistent_fieldnames()
          if inconsistent_fieldnames:
              return [
                  checks.Warning(
                      _(
                          "CONSTANCE_CONFIG_FIELDSETS is missing "
                          "field(s) that exists in CONSTANCE_CONFIG."
                      ),
                      hint=", ".join(sorted(inconsistent_fieldnames)),
                      obj="settings.CONSTANCE_CONFIG",
                      id="constance.E001",
                  )
              ]
      return []
docs: A Django system check to make sure that, if defined, CONFIG_FIELDSETS accounts for
      every entry in settings.CONFIG.