How to use the pyranges.pyranges.concat function in pyranges

def set_union(self, other, **kwargs):

        kwargs = fill_kwargs(kwargs)
        strandedness = kwargs["strandedness"]
        strand = True if strandedness else False

        if not strand:
            self = self.unstrand()
            other = other.unstrand()

        gr = pr.concat([self, other], strand)

        gr = gr.merge(strand=strand, **kwargs)

        return gr

if not overlap:
            # self = self.drop(like="__k__|__IX__")
            result = nearest#.drop(like="__k__|__IX__")
        else:
            from collections import defaultdict
            overlap_kwargs = {k: v for k, v in kwargs.items()}
            # print("kwargs ties:", kwargs.get("ties"))
            overlap_kwargs["how"] = defaultdict(lambda: None, {"first": "first", "last": "last"})[kwargs.get("ties")]
            # start = time()
            overlaps = self.join(other, **overlap_kwargs)
            # end = time()
            # print("overlaps", end - start)
            overlaps.Distance = 0
            # print("overlaps len", len(overlaps))

            result = pr.concat([overlaps, nearest])

        if not len(result):
            return pr.PyRanges()
        # print(result)
        # print(overlaps.drop(like="__").df)
        # raise

        # start = time()
        new_result = {}
        if ties in ["first", "last"]:
            # method = "tail" if ties == "last" else "head"
            # keep = "last" if ties == "last" else "first"

            for c, df in result:
                # start = time()
                # print(c)