Update npb_agent.py

npb_agent.py

@@ -5,7 +5,6 @@ from langchain_google_genai import ChatGoogleGenerativeAI
 from langchain.agents import AgentExecutor, create_tool_calling_agent, create_openai_functions_agent
 from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
 from langchain_core.messages import SystemMessage
-from constants import TAVILY_KEY
 
 # --- Custom Tools ---
 from internet_search_tool import internet_search