\DocumentMetadata{uncompress,pdfversion=2.0,testphase={phase-III,math,table},xmp=false}
\documentclass{article}
\usepackage{unicode-math}
\usepackage{luamml}
\begin{document}
\ExplSyntaxOn
\luamml_annotate:nen{1}{
nucleus = true,
core = {[0] = 'mo', 'sin'}
}{\operatorname{sin}}
\luamml_set_filename:n {test-mathml-2.txt}
\ExplSyntaxOff
$\sin x$
\end{document}