C1_W1_Lab_3_siamese-network: Lambda layer

I have a question about the model code of the output layer in the C1_W1_Lab_3_siamese-network.
It uses Lambda Layer to customize the output layer to specify euclidian_distance function for the calculation.
I understand [vect_output_a, vect_output_b] is passed into the Lambda layer for the the euclidean_distance function.
My question is about the last parameter passed into the Lambda layer, which is


For this part, don’t we need to pass some parameter into the ‘eucl_dist_output_shape’ function within the Lambda bracket?

Is it also [vect_output_a, vect_output_b] what is passed into ‘eucl_dist_output_shape’ function ? Or something else. Why we do not need to specify the variable within the Lambda?

According to the definition, we need to pass shapes into the eucl_dist_output_shape() function.
def eucl_dist_output_shape(shapes):
shape1, shape2 = shapes
return (shape1[0], 1)

An advice would be highly appreciated.

There is no siamese network in tf1 course 1 week 1.
Please move your post to the right topic.