e class environment is defined as an empty environment by <code><a href="https://rdrr.io/r/base/environment.html" class="external-link">new.env()</a></code>
at build-time, and the class descriptor is run at load-time by
<code><a href="https://rdrr.io/r/base/ns-hooks.html" class="external-link">.onLoad()</a></code>.
This ensures methods and attributes of the class is built with the
load-time (usually latest) installed dependencies (if it depends on any).
Derived classes should follow the same principle to av