C5_W4_A1_Transformer_Subclass_v1 UNQ_C5 Enconder

I am completly stuck with building the encoder. I believe I have done all the steps correct (adding training flag, splicing the pos encoding, etc…) but I still keep getting the following error, which is very undiscriptive. Any pointers in how I can complete this exercise?

Please click my name and message your notebook as an attachment.