Highlight empty check boxes on PDF

I have written a code that uses PyMuPDF to go through PDFs in a folder, search for specific words, and highlight them on the document. Now I want to expand that to include check boxes that are missing and highlight those as well. The text and boxes are selectable text - not image files. Is there a specific code I can use to include as a searchable term such as “CHECK_BOX Client” so it knows to highlight the box next to “Client” if it was missed? Thank you in advance!