I broke up with neovim....vim is my best friend now

dot_vim/plugged/vimtex/test/test-syntax/test-mhequ.tex

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+\documentclass{article}
+\usepackage{mhequ}
+
+\begin{document}
+
+\begin{equ}[onelab]
+  \sum_{i=1}^5 X_i^j X^j_i = y^j \;.
+\end{equ}
+
+\begin{equs}
+  f(x) &= \sin(x) + 1\;, \label{e:equ1}\\
+  h(x) &= f(x) + g(x) -3\;, \label{e:equ3}
+\end{equs}
+
+\begin{equs}[e:block]
+  f(x) &= \sin(x) + 1\;, \\
+  h(x) &= f(x) + g(x) -3\;,
+\end{equs}
+
+\begin{equs}
+  f(x) &= \sin(x) + 1\;, \\
+  h(x) &= f(x) + g(x) -3\;.
+\end{equs}
+
+\end{document}