python - concatenate expressions with brackets?

Question

I've stumbled across some Python expression from which I don't know whether its tensorflow or Python related. Since Im not very profound in Python, I may ask if someone could explain me, what the concatenation of (layer1)(layer2) actually means:

d = Conv2D(filters, kernel_size=f_size, strides=2, padding='same')(layer_input)
d = LeakyReLU(alpha=0.2)(d)

d is later given as an kwargs argument in the Model(*args, **kwargs). Its not a simple multiplication * operation, Ive tried that.

Thank you in advance!

question from:https://stackoverflow.com/questions/65641564/concatenate-expressions-with-brackets

Answer 1

This is not a concatenation. Those second brackets are inputs to the layer.

Conv2D(filters, kernel_size=f_size, strides=2, padding='same') returns function for which (layer_input) is input layer.