Convert list of key,value lists to dict

    [['id', 1], ['id', 2], ['id', 3], ['foo': 4]]
    {'id': [1, 2, 3], 'foo': [4]}

def list_of_lists_to_dict(l):
    """ Convert list of key,value lists to dict

    [['id', 1], ['id', 2], ['id', 3], ['foo': 4]]
    {'id': [1, 2, 3], 'foo': [4]}
    """
    d = {}
    for key, val in l:
        d.setdefault(key, []).append(val)
    return d