Update app.py

app.py

@@ -1,5 +1,6 @@
 import sys
 import subprocess
+import os
 
 def init_poetry():
     subprocess.run(["poetry", "init"])
@@ -8,7 +9,7 @@ def run_demo(llm, api_key):
     subprocess.run(["bash", "run_demo.sh", "--llm", llm, "--api_key", api_key])
 
 if __name__ == "__main__":
-    subprocess.run(["cd","pipeline"])
+    os.chdir("pipeline")
     subprocess.run(["pip","install","."])
     init_poetry()
     llm = sys.argv[1] if len(sys.argv) > 1 else "AZURE_OPEN_AI"