`MyVariantDataBuilder` raises `could not yield from a coroutine object in a non-coroutine generator`

[erikyao]

The exception is caused by builder.py#L65, when executed in Python 3.8 (su09):

yield from asyncio.sleep(0.1)

It's feasible in Python 3.6 (as explained in https://stackoverflow.com/a/64349138)

Refactoring may be needed for the set_chrom() and post_merge() methods together

[erikyao]

Fixed in commit 776df09