def concatenate(items):
    items = list(items)
    if len(items) > 1:
        return ', '.join(items[:-1]) + ' and ' + items[-1]
    elif items:
        return items[0]
    else:
        return ''
Accumulate the seen tags.
dataset/ETHPy150Open xolox/python-humanfriendly/humanfriendly/text.py/concatenate--crossover with--dataset/ETHPy150Open byt3bl33d3r/pth-toolkit/lib/python2.7/site-packages/samba/external/subunit/__init__.py/TestResultStats.tags