\cs_new_protected:Nn \stex_annotate:nn {#2}
\cs_new_protected:Nn \stex_annotate_invisible:nn {}
\cs_new_protected:Nn \stex_annotate_invisible:n {}
\cs_new_protected:Nn \_stex_annotate_force_break:n { #1 }
\NewDocumentEnvironment{stex_annotate_env} { m } {}{}
\cs_new_protected:Nn \stex_html_node:nnn {#3}
\NewDocumentEnvironment{stex_env_node} { mm } {}{}
\cs_new_protected:Nn \stex_css_link:n {}
\cs_new_protected:Nn \stex_css_literal:n {}

\prg_new_conditional:Nnn \stex_if_html_backend: {p, T, F, TF} {
  \prg_return_false:
}