Ensure consistency of 'train' argument between data generator functions

[HeQinWill]

Fixed a bug where the 'train' argument was not being consistently passed from the 'data_generator' function to the 'data_generator_list' function. This inconsistency was causing the 'train' value to unexpectedly switch to 'True' during data generation for the testing part. The 'train' argument is now directly passed from 'data_generator' to 'data_generator_list', ensuring its value remains consistent throughout the data generation process.