def join(seq, join_predicate, join):
    prev = None
    has_prev = False
    for item in seq:
        if not has_prev:
            prev = item
            has_prev = True
        else:
            if join_predicate(prev, item):
                prev = join(prev, item)
            else:
                yield prev
                prev = item

    if prev:
        yield prev

def filter_chain(filters, seq):
    for item in seq:
        for f in filters:
            if f(item):
                break
        else:
            yield item


def most_frequent_item(d): # use key in 2.5
    return max([(v, k) for k, v in d.iteritems()])[1]