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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_image_files(directory, files):
 """Recursively iterate through directory tree and list all files that have a valid image file suffix Parameters directory : directory Path to directory on disk files : List(string) List of file names Returns ------- List(string) List of files that have a valid image suffix """

    # For each file in the directory test if it is a valid image file or a
    # sub-directory.
    for f in os.listdir(directory):
        abs_file = os.path.join(directory, f)
        if os.path.isdir(abs_file):
            # Recursively iterate through sub-directories
            get_image_files(abs_file, files)
        else:
            # Add to file collection if has valid suffix
            if '.' in f and '.' + f.rsplit('.', 1)[1] in VALID_IMGFILE_SUFFIXES:
                files.append(abs_file)
    return files