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

def _paths_to_cats(paths, scheme):
    """Extract out fields and labels from directory names"""
    # can be factored out in fastparquet
    from fastparquet.util import ex_from_sep, val_to_num, groupby_types

    cats = OrderedDict()
    raw_cats = OrderedDict()

    for path in paths:
        s = ex_from_sep("/")
        if scheme == "hive":
            partitions = s.findall(path)
            for key, val in partitions:
                cats.setdefault(key, set()).add(val_to_num(val))
                raw_cats.setdefault(key, set()).add(val)
        else:
            for i, val in enumerate(path.split("/")[:-1]):
                key = "dir%i" % i
                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):

def _paths_to_cats(paths, scheme):
    """Extract out fields and labels from directory names"""
    # can be factored out in fastparquet
    cats = OrderedDict()
    raw_cats = OrderedDict()

    for path in paths:
        s = ex_from_sep("/")
        if scheme == "hive":
            partitions = s.findall(path)
            for (key, val) in partitions:
                cats.setdefault(key, set()).add(val_to_num(val))
                raw_cats.setdefault(key, set()).add(val)
        else:
            for (i, val) in enumerate(path.split("/")[:-1]):
                key = "dir%i" % i
                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):