Normalize input to `list` properly in `normalize_args`

Currently, if a user wants to partition along column “x”, and since columns are unique, thinks it is appropriate to provide a set as the value to the argument e.g. partition_on={"x"}; this would be “normalized” to [{"x"}] ( a list of sets), and then an error will be raised at some other part of the code where this input is unexpected. The expected behavior of the normalization would be to normalize sets, tuples or similar iterables to a list such as ["x"] (a list of strings).

I do not consider this a bug as in the docs it states partition_on should be provided as a list.

Normalization function: kartothek.io_components.utils.normalize_arg

[fjetter]

Sets can not be properly normalized since they don’t preserve order. For ‘partition_on’ the order is quite important, i.e. a set would be an incompatible input

[lr4d]

Hint: the following could be a start to parse (0,1) to [0,1] instead of the current [(0,1)].

def _make_list(x):
    if isinstance(x, (str, bytes)):
        return [x]
    return list(x)

    elif old_value is None:
        new_value = _ARGS_TO_TYPE[arg_name]()