To factor the error checking, use importChecked instead of importSeq. This
avoids repeating the names of all of the imported child nodes once, and allows
errors to be checked with a single conditional as it is with importSeq.
peak memory: 601.63MB real: 0m19.172s obj size: 8,352kb
peak memory: 954.11MB real: 0m26.188s obj size: 10,000kb
The speed is not as impressive as I hoped, but the memory use reduction
is impressive, and seems worth it.