def _get_idx(self, el: str) -> int:
for e in (el, el.lower(), el.capitalize(), el.upper()):<EOL><INDENT>if e in self.token2idx_dict:<EOL><INDENT>return self.token2idx_dict[e]<EOL><DEDENT><DEDENT>return <NUM_LIT:1><EOL>
Returns idx for el (token or char).

        Args:
            el: token or character

        Returns:
            idx in vocabulary