Looking through different Python modules I have several times seen that classes are used to define a collection of valid arguments and I wonder what the purpose of this approach is.

E.g. consider the following class:

class ArgumentOption:
    ARG1 = "ARG1"
    ARG2 = "ARG2"
    ARG3 = 3

What is the purpose of this approach as opposed to just defining a set, list, tuple, or something else containing the same options? Many times I see that functions might as well have take a string, int or whatever as argument instead of an instance of a class as defined above.