pikepdf: page.images is empty

I’m trying to resize only images with large resolution in a document. I’ve been told that the attached document has such images. page.images doesn’t show me any image. Am I doing something wrong?

test.pdf

from pikepdf import Pdf, PdfImage, Name
doc = Pdf.open('test.pdf')
page = doc.pages[0]
print(list(page.images.keys()))