First of all, please see this thread.
There are 6 outputs in a list. That’s a\_G. For the style cost calculation, we need to handle 5 outputs in a list. On the other hand, “compute_layer_style_cost()” is for one single layer (output) which is unpacked from a list. (In this sense, if you pass this list to “compute_layer_style_cost()”, then, the above error should occur.)
In stead, you need to call other function which actually calls “compute_layer_style_cost()” with unpacking a list.
Hope this helps.