Enhance app.py by importing the 'os' module for improved environment variable handling. This change supports better configuration management in the application.

app.py

@@ -4,6 +4,7 @@ from langchain.memory import ConversationBufferMemory
 from transformers import AutoTokenizer, AutoModelForCausalLM, pipeline
 import PyPDF2
 from dotenv import load_dotenv
+import os
 
 # Load environment variables from .env
 load_dotenv()