new_contents: from functools import wraps
  from flask import flash, redirect, url_for, session
  from app import views
  
  def login_required(f):
      @wraps(f)
      def decorated_function(*args, **kwargs):
          if 'logged_in' in session:
              return f(*args, **kwargs)
          else:
              flash("Please login to continue.", "danger")
              return redirect(url_for("login"))
      return decorated_function
subject: Create a decorator `login_required` for access control on pages for logged in users.