@property<EOL><INDENT>def allow_extend(self):<DEDENT>
return self._allow_extend<EOL>
Allow extension of the TokenEmbedding with new tokens.

        If True, `TokenEmbedding[tokens] = vec` can introduce new tokens that
        were previously unknown. New indices will be assigned to the newly
        introduced tokens. If False, only known tokens can be updated.

        Returns
        -------
        bool:
            Extension of the TokenEmbedding is allowed.