[Answered ]-Lambda – 'QuerySet' object has no attribute 'xxx'

You’re doing something like:

>>> bs, jn = [1, 2], [3, 4]
>>> list(itertools.chain(x for x in [bs, jn]))
[[1, 2], [3, 4]]

What you want do is:

>>> list(itertools.chain(bs, jn))
[1, 2, 3, 4]

So, you need to change joined = itertools.chain ... line as follow:

joined = itertools.chain(bs, jn)