Issue accessing PDFViewerApplication with npm package

[calmHeaven]

I'm facing this issue where I'm unable to override the save function for uploading to the cloud because the package doesn't seem to contain the PDFViewerApplication class (which contains the .save() function), but when I check the viewer.js here on the repo it appears to be here. Is there a reason why? And if so how do I get around this without forking the repo?