It looks like you made the classic mistake of adding commas onto the end of the lines when you are using the Functional Model, instead of the Sequential Model. You need the commas in the Sequential case, but they are a disaster in the Functional Case. If you say:
myOutputTensor = myLayerFunction(myInputTensor),
That comma on the end turns the output of the RHS into a “tuple” with one more dimension than the base tensor that was returned by the function.
Here’s a great thread to read for more details on how to use the two styles of layer programming in TF/Keras.