Sequencing is when you traverse over a collection's identity. It's not obvious but the purpose is to go from
xs.sequence == xs.traverse(identity)
It's a great idea to internalize the following:
xs.map(f).sequence == xs.map(f).traverse(identity) == xs.traverse(f)
The reason this is so is because
sequence are defined in terms of traverse in Cats.
When you find yourself flattening after a traverse, use