Creates a dataset of paired images from a directory.

The dataset should be partitioned into two sets: one contains images that

will have the low pass filter applied, and the other contains images that

will have the high pass filter applied.

Args:

path: string specifying the directory containing images

Returns:

images$\_$a: list of strings specifying the paths to the images in set A$,$

in lexicographically$-$sorted order

Filter out image paths that have $"$a$"$ before $"\_"$ in their names, sort them and store in images$\_$a

For Eg: Image names such as $"1$a$\_$dog.bmp$","2$a$\_$motorcycle.bmp$","3$a$\_$plane.bmp$"....$ should go in images$\_$a

images$\_$b: list of strings specifying the paths to the images in set B$,$

in lexicographically$-$sorted order

Filter out image paths that have $"$b$"$ before $"\_"$ in their names, sort them and store in images$\_$b

For Eg: Image names such as $"1$b$\_$cat.bmp$","2$b$\_$bicycle.bmp$","3$b$\_$bird.bmp$"....$ should go in images$\_$b