Look at the import cell to see what they imported as Conv2D. You’ll find that it’s a Keras “Layer” function, a subclass of Layer. When you call that function with the parameters you want (shapes, number of filters, padding and so forth), it returns you a function. Then you call that function with a Tensor as input, which is why there are two sets of parentheses. But I see you’ve already seen this thread from ai_curious which goes through all that in detail.
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