🔧 Fix 'str expected, not NoneType' startup error

✅ Problem solved:
• Fixed LANGFUSE environment variable assignment in knowledge_graph_tester.py
• Added null checks before setting os.environ values
• Only set env vars when values are not None

🎯 Root cause:
• Lines 40-41 unconditionally set LANGFUSE_PUBLIC_KEY/SECRET_KEY to environ
• These could be None, causing TypeError in os.environ assignment
• Added proper null validation

⚡ Result:
• Backend server now starts successfully
• No more TypeError: str expected, not NoneType
• Ready for HF Spaces deployment

.gitignore

@@ -0,0 +1,9 @@
+__pycache__/
+*.py[cod]
+*.class
+logs/
+*.log
+datasets/
+db/
+cache/
+evaluation_results/

agentgraph/testing/knowledge_graph_tester.py

@@ -30,15 +30,19 @@ logger = logging.getLogger(__name__)
 # Import LiteLLM
 from litellm import completion
 
-# API Key setup
-os.environ["OPENAI_API_KEY"] = OPENAI_API_KEY
+# API Key setup - only set if value exists
+if OPENAI_API_KEY:
+    os.environ["OPENAI_API_KEY"] = OPENAI_API_KEY
 DEFAULT_MODEL = "gpt-4.1-mini"
 
 
 from utils.config import LANGFUSE_PUBLIC_KEY, LANGFUSE_SECRET_KEY, LANGFUSE_AUTH, LANGFUSE_HOST
 
-os.environ["LANGFUSE_PUBLIC_KEY"] = LANGFUSE_PUBLIC_KEY
-os.environ["LANGFUSE_SECRET_KEY"] = LANGFUSE_SECRET_KEY
+# Only set environment variables if they have values (not None)
+if LANGFUSE_PUBLIC_KEY:
+    os.environ["LANGFUSE_PUBLIC_KEY"] = LANGFUSE_PUBLIC_KEY
+if LANGFUSE_SECRET_KEY:
+    os.environ["LANGFUSE_SECRET_KEY"] = LANGFUSE_SECRET_KEY
 
 
 if LANGFUSE_PUBLIC_KEY and LANGFUSE_SECRET_KEY: