fd = {}
fo = {'yandex.ru': ['page-url', 'wmode', 'wv-type', 'wv-hit', 'wv-part', 'wv-check', 'browser-info']}

def add(form, fdict):
    dom = form.keys()[0]
    if dom in fdict.keys():
        if form[dom] not in fdict[dom]:
            fdict[dom].append(form[dom])
    else:
        fdict[dom] = [form[dom]]
    return fdict
fd = add(fo, fd)
print(fd)