start_model_file = get_model_files_for_suffix(start_model_files, args.get_epoch_save_start_suffix())[0] IndexError: list index out of range

This error occurs when the code tries to access an element in a list using an index that is out of bounds. In this case, the list `start_model_files` does not have any elements with the suffix specified by `args.get_epoch_save_start_suffix()`, so the code is unable to retrieve the desired model file.

To fix this error, you can check if the list `start_model_files` contains any elements with the desired suffix before trying to access them with an index. For example, you can modify the code like this:

start_model_files = get_model_files_for_prefix(args.start_model_prefix)
start_model_file_suffix = args.get_epoch_save_start_suffix()
start_model_file = None
for file in start_model_files:
    if file.endswith(start_model_file_suffix):
        start_model_file = file
        break
if start_model_file is None:
    # handle the case where no model files were found with the desired suffix
else:
    # continue with the code that uses start_model_file

This code iterates over the list `start_model_files` and checks each file to see if it ends with the desired suffix. If a file is found with the desired suffix, it is stored in the variable `start_model_file`. If no files are found with the desired suffix, you can handle this case appropriately (for example, by raising an error or using a default model file).