I have a css snippet. When I add
---
cssclass: p_indent
---
it, correctly, indents each paragraph in the markdown preview.
I also added this code so that when I export to pdf, it also indents the paragraphs. Unfortunately, it indents paragraphs regardless of whether the file has the cssclass p_indent.

How can I edit the above code so that only exported files with the p_indent cssclass get indented paragraphs?