Hello Thank you for good research!! I wonder what means words (C, con_up, con_down, cluster, layer) in JSON file. In v1_1_train_nus.json, words (C, con_up, con_down, cluster, layer) are "null", Is it have any reaseon? ------ v1_1_train_nus.json ------  ------ drivelm_carla_vqas ------ 