Update app.py

app.py

@@ -227,7 +227,7 @@ def neural_networks():
 st.sidebar.header("📚 Contents")
 
 # Show Introduction first in the sidebar
-intro_option = st.sidebar.radio("📚 Introduction", ["Introduction"])
+intro_option = st.sidebar.radio("📚 Introduction", ["Introduction", "Select a Topic"])
 
 # Grouping the types of machine learning into one section
 types_of_ml = st.sidebar.radio("📊 Types of Machine Learning",