def format_live_refs(ignore=NoneType):
    """Return a tabular representation of tracked objects"""
    s = "Live References\n\n"
    now = time()
    for cls, wdict in sorted(six.iteritems(live_refs),
                             key=lambda x: x[0].__name__):
        if not wdict:
            continue
        if issubclass(cls, ignore):
            continue
        oldest = min(six.itervalues(wdict))
        s += "%-30s %6d   oldest: %ds ago\n" % (
            cls.__name__, len(wdict), now - oldest
        )
    return s
Return a tabular representation of tracked objects
stackoverflow/venv/lib/python3.6/site-packages/scrapy/utils/trackref.py