def get_unk_id(self, type_name):
    """Return the unknown symbol id with given name, or None if nonexistent."""
    if not self.is_type(type_name):
      raise TypeNameError(type_name, 'Type is not defined.')
    return self._symtab[type_name].get_unk_id()
Return the unknown symbol id with given name, or None if nonexistent.
language/nql/nql/__init__.py