Is it possible to include package structure to a flutter project documentation?

Question

I use dartdoc to generate documentation of a Flutter project. The documentation is generated, but there is no structure to it.

For example if I have file structure like this

• DirA
  • Dir1
    • Widget1
    • Widget2
  • Widget3
• Widget4

The documentation stucture looks like this

• Widget1
• Widget2
• Widget3
• Widget4

How can I introduce structure to the documentation? Is it even possible? I did not find any solution. I tried to add <package_name>.dart file to every directory with exports only, but that did not help.