def process_input_dir(input_dir):
    """ 
    Find all image file paths in subdirs, convert to str and extract labels from subdir names
    :param input_dir Path object for parent directory e.g. train
    :returns: list of file paths as str, list of image labels as str
    """
    file_paths = list(input_dir.rglob('*.png'))
    
    file_path_strings = [str(path) for path in file_paths]
    label_strings = [path.parent.name for path in file_paths]
    
    return file_path_strings, label_strings