How to use the fastparquet.util.groupby_types function in fastparquet

cats.setdefault(key, set()).add(val_to_num(val))
                raw_cats.setdefault(key, set()).add(val)

    for key, v in cats.items():
        # Check that no partition names map to the same value after
        # transformation by val_to_num
        raw = raw_cats[key]
        if len(v) != len(raw):
            conflicts_by_value = OrderedDict()
            for raw_val in raw_cats[key]:
                conflicts_by_value.setdefault(val_to_num(raw_val), set()).add(raw_val)
            conflicts = [
                c for k in conflicts_by_value.values() if len(k) > 1 for c in k
            ]
            raise ValueError("Partition names map to the same value: %s" % conflicts)
        vals_by_type = groupby_types(v)

        # Check that all partition names map to the same type after
        # transformation by val_to_num
        if len(vals_by_type) > 1:
            import warnings

            examples = [x[0] for x in vals_by_type.values()]
            warnings.warn(
                "Partition names coerce to values of different"
                " types, e.g. %s" % examples
            )
    return {k: list(v) for k, v in cats.items()}

cats.setdefault(key, set()).add(val_to_num(val))
                raw_cats.setdefault(key, set()).add(val)

    for (key, v) in cats.items():
        # Check that no partition names map to the same value after
        # transformation by val_to_num
        raw = raw_cats[key]
        if len(v) != len(raw):
            conflicts_by_value = OrderedDict()
            for raw_val in raw_cats[key]:
                conflicts_by_value.setdefault(val_to_num(raw_val), set()).add(raw_val)
            conflicts = [
                c for k in conflicts_by_value.values() if len(k) > 1 for c in k
            ]
            raise ValueError("Partition names map to the same value: %s" % conflicts)
        vals_by_type = groupby_types(v)

        # Check that all partition names map to the same type after
        # transformation by val_to_num
        if len(vals_by_type) > 1:
            examples = [x[0] for x in vals_by_type.values()]
            warnings.warn(
                "Partition names coerce to values of different"
                " types, e.g. %s" % examples
            )
    return {k: list(v) for k, v in cats.items()}