The `cond` of the `tf.while_loop`.

def _cond(self, unused_x, unused_cumul_out, unused_prev_state,
            unused_cumul_state, cumul_halting, unused_iteration,
            unused_remainder):
    """The `cond` of the `tf.while_loop`."""
    return tf.reduce_any(cumul_halting < 1)