Superfluous shortcut sensitivities are being created when override_sensitivity() method is implemented
Customized sensitivities are presently broken. Therefore, if we want to compute \frac{\partial A}{\partial D}
on a simple graph like this:
graph TD;
A-->B;
A-->C;
B-->D;
C-->D;
where A implements a custom sensitivity, then no fields for \frac{\partial B}{\partial D}
or \frac{\partial C}{\partial D}
should be allocated.
Unfortunately, results from the tests on this weren't being properly aggregated into the sensitivity test results, so they were giving false passes.