For training and testing, your directory structure should look like this
Datasets
ββββtrain
ββββββββDPDD
βββββββββββββinputL_crops
βββββββββββββinputR_crops
βββββββββββββinputC_crops
βββββββββββββtarget_crops
ββββval
ββββββββDPDD
βββββββββββββinputL_crops
βββββββββββββinputR_crops
βββββββββββββinputC_crops
βββββββββββββtarget_crops
ββββtest
ββββββββDPDD
βββββββββββββinputL
βββββββββββββinputR
βββββββββββββinputC
βββββββββββββtarget