try using partial to partially format the system prompt

chain.py

@@ -2,6 +2,7 @@ import os
 import mlflow
 import datetime
 import streamlit as st
+from functools import partial
 from operator import itemgetter
 from langchain_huggingface import HuggingFaceEmbeddings
 from langchain_databricks.vectorstores import DatabricksVectorSearch
@@ -100,7 +101,7 @@ class ChainBuilder:
         # Prompt Template for generation
         prompt = ChatPromptTemplate.from_messages(
             [
-                ("system", self.llm_config.get("llm_prompt_template").format(date_str=datetime.datetime.now().strftime("%B %d, %Y"))), # add current date to the date_str var in system prompt
+                ("system", partial(self.llm_config.get("llm_prompt_template").format, date_str=datetime.datetime.now().strftime("%B %d, %Y"))), # add current date to the date_str var in system prompt
                 # *** Note: This chain does not compress the history, so very long converastions can overflow the context window. TODO
                 # We need to at some point chop this history down to fixed amount of recent messages
                 MessagesPlaceholder(variable_name="formatted_chat_history"),