def is_subdirectory(path_a, path_b):
path_a = os.path.realpath(path_a)<EOL>path_b = os.path.realpath(path_b)<EOL>relative = os.path.relpath(path_a, path_b)<EOL>return (not relative.startswith(os.pardir + os.sep))<EOL>
Returns True if `path_a` is a subdirectory of `path_b`.