code: def gravatar(self, size=20):
          
          default = "mm"
  
          gravatar_url = "//www.gravatar.com/avatar/" + hashlib.md5(self.email.lower()).hexdigest() + "?"
          gravatar_url += urllib.urlencode({'d': default, 's': str(size)})
  
          return gravatar_url
docs: Construct a gravatar image address for the user