ValueError: Layer conv2d_1 was called with an input that isn't a symbolic tensor. Received type: . Full input: [(600, 600, 3)]. All inputs to the layer should be tensors.

加载模型，也就是如下操作：

发现报错：

经过反复查看代码并运行，发现代码中已经封装好了模型,即函数中return model

也就意味着在if __name__ == '__main__':中直接将已经封装好的模型赋予你要可视化的模型就好，
即

又或者是ValueError: Unexpectedly found an instance of type <class 'tuple'>. Expected a symbolic tensor instance.
这种错误也既有可能是上述原因