test: test for make_engines that are aliases referring to a sequence of variants.
###################
Users' Flow Diagram
###################
.. raw:: html
<img src="images/user-graph.dot.png" alt="Flow Diagram" usemap="#flowdiagram" style="border-style: none"/>
<map name="flowdiagram" id="flowdiagram">
.. raw:: html
:file: user-graph.dot.cmap
.. raw:: html
</map>