code: def _validate_tileset(self, tileset):
          
          if '.' not in tileset:
              tileset = "{0}.{1}".format(self.username, tileset)
  
          pattern = '^[a-z0-9-_]{1,32}\.[a-z0-9-_]{1,32}$'
          if not re.match(pattern, tileset, flags=re.IGNORECASE):
              raise ValidationError(
                  'tileset {0} is invalid, must match r"{1}"'.format(
                      tileset, pattern))
  
          return tileset
docs: Validate the tileset name and
          ensure that it includes the username