def lm_mask(s):
    seq_len = K.shape(s)[1]
    idxs = K.arange(0, seq_len)
    mask = (idxs[None, :] <= idxs[:, None])
    mask = K.cast(mask, K.floatx())
    return ((- (1 - mask[(None, None)])) * 1000000000000.0)
def lm_mask(s):
    seq_len = K.shape(s)[1]
    idxs = K.arange(0, seq_len)
    mask = (idxs[None, :] <= idxs[:, None])
    mask = K.cast(mask, K.floatx())
    return ((- (1 - mask[(None, None)])) * 1000000000000.0)