In this case it is simply a function to load an image:
def default_loader_unaligned(path):
    """
    Helper function to load an Image with PIL
    :param path: path of image file
    :return: loaded image in RGB mode as PIL Image
    """
    return Image.open(path).convert('RGB')

You can modify this function however to perform some transformations and if you need to load aligned image data it should be modified to return a tuple of image and label