def concat(xss):
return list(anytemplate.compat.from_iterable(xs for xs in xss))<EOL>
>>> concat([[]])
[]
>>> concat((()))
[]
>>> concat([[1,2,3],[4,5]])
[1, 2, 3, 4, 5]
>>> concat([[1,2,3],[4,5,[6,7]]])
[1, 2, 3, 4, 5, [6, 7]]
>>> concat(((1,2,3),(4,5,[6,7])))
[1, 2, 3, 4, 5, [6, 7]]
>>> concat(((1,2,3),(4,5,[6,7])))
[1, 2, 3, 4, 5, [6, 7]]
>>> concat((i, i*2) for i in range(3))
[0, 0, 1, 2, 2, 4]