chore: update self-sim function errors

Signed-off-by: Suvaditya Mukherjee <suvadityamuk@gmail.com>

demos/pipeline_fn.py

@@ -549,9 +549,9 @@ class GuideFlow3dPipeline:
         structure_mesh: str,
         convert_target_yup_to_zup: bool,
         output_dir: str,
-        appearance_text: str,
-        appearance_image: str,
         app_type: str,
+        appearance_text: Optional[str] = None,
+        appearance_image: Optional[str] = None,
     ) -> Optional[str]:
         _ = self.preprocess(
             structure_mesh=structure_mesh,