TVM on Ubuntu withon NNVM

Using TensorFlow backend.
Traceback (most recent call last):

File “tvm_keras_compile.py”, line 8, in
graph, params = nnvm.frontend.from_keras(“resnet50_weights.h5”)

File “/tvm/nnvm/python/nnvm/frontend/keras.py”, line 674, in from_keras
assert isinstance(model, keras.engine.training.Model)

AssertionError

My keras version is 2.2.4,tensorflow version is 1.13.1