How to use the duecredit.io.PickleOutput.load function in duecredit

def run(args):
    from ..io import PickleOutput
    if not os.path.exists(args.filename):
        lgr.debug("File {0} doesn't exist.  No summary available".format(
            args.filename))
        return 1

    due = PickleOutput.load(args.filename)
    #CollectorSummary(due).dump()

    if args.format == "text":
        out = TextOutput(sys.stdout, due, args.style)
    elif args.format == "bibtex":
        out = BibTeXOutput(sys.stdout, due)
    else:
        raise ValueError("unknown to treat %s" % args.format)
    out.dump()

def load_due(filename):
    return PickleOutput.load(filename)