updated frontend app script

frontend.py

@@ -8,7 +8,7 @@ import streamlit as st
 from PIL import Image
 from skimage.io import imread
 
-def infer():
+def infer() -> None:
     st.title("Overhead MNIST classification app")
 
     # select an input image file
@@ -42,7 +42,7 @@ def infer():
         st.write(response.json())
     return
 
-def app_info():
+def app_info() -> None:
     st.title("App info")
     st.markdown("_Task - Overhead MNIST classification_")
     st.markdown("_Project repo - [https://github.com/AbhishekRS4/overhead_mnist](https://github.com/AbhishekRS4/overhead_mnist)_")
@@ -59,12 +59,12 @@ app_modes = {
     "Overhead MNIST Inference App": infer,
 }
 
-def start_app():
+def start_app() -> None:
     selected_mode = st.sidebar.selectbox("Select mode", list(app_modes.keys()))
     app_modes[selected_mode]()
     return
 
-def main():
+def main() -> None:
     start_app()
     return