input: Write a python function to start a Flask web server that returns 'Welcome!' on the home route.
  assert get_home_route_response() == 'Welcome!'
  assert isinstance(get_home_route_response(), str)
output: def start_flask_server():
      from flask import Flask
  
      app = Flask(__name__)
  
      @app.route('/')
      def home():
          return 'Welcome!'
  
      return app
  
  def get_home_route_response():
      app = start_flask_server()
      with app.test_client() as client:
          response = client.get('/')
          return response.data.decode()