fix yaml parse error

Use re to handle the unexpected conversion of colons in the yaml format

cookbook/pocketflow-workflow/nodes.py

@@ -1,3 +1,4 @@
+import re
 from pocketflow import Node, BatchNode
 from utils import call_llm
 import yaml
@@ -21,6 +22,11 @@ sections:
 ```"""
         response = call_llm(prompt)
         yaml_str = response.split("```yaml")[1].split("```")[0].strip()
+        yaml_str = re.sub(
+            r'(?m)^(\s*)-\s*([^"\n]+)',
+            r'\1- "\2"',
+            yaml_str
+        )
         structured_result = yaml.safe_load(yaml_str)
         return structured_result