fix: Typo

Where type checking would save me

app.py

@@ -37,7 +37,7 @@ predict_and_write(
     step_size=128,
     dummy=5,
     # max_dist,
-    val_cols=["obs" "exp" "pval"],
+    val_cols=["obs", "exp", "pval"],
     # keep_zeros,
 )