old_contents: # -*- conding: utf-8 -*-
  import os
  
  import jinja2
  import webapp2
  
  import utils
  
  JINJA_ENV = jinja2.Environment(
      loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
      autoescape=True)
  
  
  class BaseHandler(webapp2.RequestHandler):
      def render(self, template, **kw):
          """Method render takes a template file and key-value pairs.
  
          It substitutes keys found in template with values in pairs.
          The resulted page is sent back to user."""
          t = JINJA_ENV.get_template(template)
          self.response.write(t.render(kw))
  
      def set_cookie(self, user):
          """Set user cookie in headers."""
          cookie = utils.make_cookie(user)
          self.response.headers.add_header(
              'Set-Cookie',
              'user={}; Path=/'.format(cookie))
  
      def logout(self):
          """Set user cookie to empty in headers."""
          self.response.headers.add_header('Set-Cookie',
                                           'user=;Path=/')
  
new_contents: # -*- conding: utf-8 -*-
  import os
  
  import jinja2
  import webapp2
  
  import utils
  
  JINJA_ENV = jinja2.Environment(
      loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
      autoescape=True)
  
  
  class BaseHandler(webapp2.RequestHandler):
      def render(self, template, **kw):
          """Method render takes a template file and key-value pairs.
  
          It substitutes keys found in template with values in pairs.
          The resulted page is sent back to user."""
          t = JINJA_ENV.get_template(template)
          self.response.write(t.render(kw))
  
      def set_cookie(self, user):
          """Set user cookie in headers."""
          cookie = utils.make_cookie(user)
          self.response.headers.add_header(
              'Set-Cookie',
              'user={}; Path=/'.format(cookie))
  
      def logout(self):
          """Set user cookie to empty in headers."""
          self.response.headers.add_header('Set-Cookie',
                                           'user=;Path=/')
  
      def get_username(self):
          """Check if user has a valid cookie.
          Returns username if cookie is valid."""
          cookie = self.request.cookies.get('user')
          if cookie and utils.valid_cookie(cookie):
              username = cookie.split('|')[0]
              return username
  
subject: Add a method to get username if users have valid cookie