Post project invoice proposal using code

Hi experts,

I have made an import function in AX 3.0, that can make a project invoice proposal.

Now I need to post the proposal.

When I look at pages like this

I should use this code:

projFormLetter = ProjFormLetter::construct(DocumentStatus::ProjectInvoice);


But the construct method is private, so I cannot use that.

How do I program that posting?

Look at which public methods call construct().