R keras模型评估/预测错误：do.call（object $ evaluate，args）中的错误：“ what”必须是函数或字符串

Question

我有一个keras模型（使用R）和TF作为后端，如下

history <- model %>% fit( train_X1,train_y,batch_size=100,
               epochs=80,validation_split = 0.2,
               shuffle=TRUE)

> class(model)
[1] "keras.models.Sequential"         "keras.engine.training.Model"    
[3] "keras.engine.topology.Container" "keras.engine.topology.Layer"    
[5] "python.builtin.object"                

尺寸如下：

> dim(train_X1)
[1] 4893   64   64    1
> dim(train_y)
[1] 4893   12

我想先在火车上评估，然后在测试中预测。

model %>% evaluate(train_X1,train_y)
pred <- model %>% predict_classes(train_X1)

但是在运行评估命令时出现以下错误：

Error in do.call(object$evaluate, args) :  'what' must be a function or character string

任何帮助将不胜感激。谢谢