input: Write a python function to create a Flask app with a homepage and a form that accepts an email and displays it.
  assert create_flask_app() is not None
  assert isinstance(create_flask_app().url_map, object)
  assert create_flask_app().test_client().post('/form', data={'email': 'test@example.com'}).status_code == 200
output: def create_flask_app():
      from flask import Flask, request, render_template_string
  
      app = Flask(__name__)
  
      @app.route('/')
      def home():
          return render_template_string('''
              <form action="/form" method="post">
                  <label for="email">Email:</label>
                  <input type="email" id="email" name="email">
                  <input type="submit" value="Submit">
              </form>
          ''')
  
      @app.route('/form', methods=['POST'])
      def form():
          email = request.form['email']
          return f'Email: {email}'
  
      return app