pylint fixes

Author: Ragini-Microsoft

src/backend/orchestrator.py

@@ -15,15 +15,13 @@
 Agents can hand off to each other dynamically based on context.
 """
 
-import base64
 import json
 import logging
 import re
 from typing import AsyncIterator, Optional, cast
 
 from agent_framework import (
     Message,
-    WorkflowEvent,
 )
 from agent_framework.orchestrations import HandoffBuilder, HandoffAgentUserRequest
 from agent_framework.azure import AzureOpenAIResponsesClient, AzureAIProjectAgentProvider