How do I find out the name from a Principal Id when using pnp sp?

Question

I need to find out the username or name of a principalId number that I'm returning from a REST call which get's role assignments currently on a SharePoint list item.

I understand it may involve:

const r = await sp.web.lists.getByTitle('MyList').items.getById(theItem).roleAssignments() 

There is no documentation that explains how to do this that I have found.

Answer 1

Answered my own question again:

const assignments = await sp.web.lists.getByTitle('MyList').items.getById(theItem).roleAssignments();

const expanded = assignments[0].PrincipalId;

console.log(expanded, 'expanded');