dump_yaml does not dump new attributes you have added to a settings file

[NurullahMorshed]

I am trying to manipulate the settings files for my CI pipeline. I can modify settings that already exist, but when I try to load a new setting attribute, it lets me add it to the entry, but when I run dum_yaml command, only settings attributes that already exist are changed. The new settings I have added are not in the file.

Specifically, I am manipulating the IL2CPP settings and trying to protect against a situation where someone has not enabled il2cpp and is missing the settings in the project settings file.

Steps to reproduce:

1. project_settings_file = 'UnityProject/ProjectSettings/ProjectSettings.asset'
2. doc = UnityDocument.load_yaml(project_settings_file)
3. ProjectSettings = doc.entry
4. ProjectSettings.testAttribute = {}
5. ProjectSettings.testAttribute
6. ProjectSettings.testAttribute["Test"] = "1"
7. ProjectSettings.testAttribute["Test"]
8. doc.dump_yaml()
9. Open ProjectSettings file

Expected Results:
Project settings file has a new entry called testAttribute with a value of Test = 1