\__unravel_begin_insert_or_adjust: is undefined

[muzimuzhi]

When unravel-ing \footnote, the \insert used inside \@footnotetext raises

! Undefined control sequence.
\__unravel_cmd_37: ...vel_begin_insert_or_adjust:

l.6 content\unravel{\footnote{abc}}

Currently \insert is not marked as "not implemented", hence \__unravel_begin_insert_or_adjust: is expected as implemented.

Example:

% unravel-footnote.tex
\documentclass{article}
\usepackage{unravel}

\begin{document}
content\unravel{\footnote{abc}}
\end{document}

Run it with pdflatex unravel-footnote, then input u\@footnotetext followed by three "Enter"s.