refactor: move hello() function to hello.py and import it in app.py

app.py

@@ -1,6 +1,7 @@
 import os
 import subprocess
 from flask import Flask, render_template, Response, request, jsonify
+from hello import hello
 
 app = Flask(__name__)
 

hello.py

@@ -0,0 +1,4 @@
+def hello():
+    "print a greeting"
+
+    print("hello")