code: def validate_key(self, activation_key):
          
          try:
              username = signing.loads(
                  activation_key,
                  salt=self.key_salt,
                  max_age=conf.get('ACCOUNT_ACTIVATION_DAYS') * 86400
              )
              return username
          # SignatureExpired is a subclass of BadSignature, so this will
          # catch either one.
          except signing.BadSignature:
              return None
docs: Verify that the activation key is valid and within the
          permitted activation time window, returning the username if
          valid or ``None`` if not.