escape line in code format

app.py

@@ -219,7 +219,7 @@ def str_to_md(text):
 
     lines = text.split('\n')
     lines = [escape_hash(line) for line in lines]
-    return '  \n'.join(l if not all(c == '-' for c in l) else '-'*len(l) for l in lines)
+    return '  \n'.join(l if not all(c == '-' for c in l) else '_'*len(l) for l in lines)
 
 def text_to_text_generation(verbose, prompt):
     prompt = prompt.strip()