Update modelling_longitudinal.py

Fixed issues with attn_implementation and decoder_inputs['past_key_values'].

modelling_longitudinal.py

@@ -127,6 +127,7 @@ class LongitudinalPromptMultiCXREncoderDecoderModel(VisionEncoderDecoderModel):
             encoder = MultiCvtWithProjectionHead(config=config.encoder)
 
         # Decoder:
+        config.decoder._attn_implementation = 'eager'
         if decoder is None:
             decoder = transformers.BertLMHeadModel(config=config.decoder)