Real groupby of python itertools

pyhon_realgroupby.py

def realgroupby(it, key):
    from itertools import groupby, chain
    d = {}
    for k, ii in groupby(it, key):
        if k in d:
            d[k] = chain(d[k], list(ii))
        else:
            d[k] = list(ii)
    return d