generator function is broken.
When I run this,
var pipedSeq = pipeSeq(rangeSeq, 2, 3) // 2, 5, 8, 11
.pipeline(accumulator) // 2, 7 (5+2), 15(7+8), 26(15+11)
.invoke();
var seq = generator(pipedSeq);
console.log(seq);

it prints '{ next: 2 }', and testcase fails with error,
TypeError: seq.next is not a function
at begin
at Object.it...

If i reimplement the generator, the sample testcase passes. However attempt call still fails and hence i cannot submit my answer.
Please fix this.

Is this one working?
I'm able to run the sample test cases (completed in 538ms), but the attempt request always fails with network error.