Mappings of modules from their in-language URI, to their resolved URI.
A module's in-language URI is the form used within Pkl source code.
For example, modulepath-based modules have form modulepath:/path/to/my/module.pkl.
A module's resolved URI is the form used to load the module's contents.
The same modulepath module might have form
jar:file:///path/to/file.zip!/path/to/my/module.pkl if Pkl run with
--module-path /path/to/file.zip.
Dependency-notation imports, such as "@myPackage/myModule.pkl", are represented as
in-language URIs with scheme projectpackage:.
In the case of local project dependenecies, they will be local URIs resolved from the project
file URI (in normal cases, file: URIs).
The graph of imports declared (directly and transitively) by the modules passed to
importGraph().