Instantiate FileSystem Template.
The sections of the chapter represent the available filesystem trees that can be instantiated.
os
sys
process
files
txt
document
pairs
pairs(items)
mapping
mapping(content)
transform
transform(tree, section)
emit
emit(route, data)
Store a template into the given route.
instantiate
instantiate(target, source, section)
mainprocess.Exit
main(inv)