Show the function for the correlation plot

Consistent with the other scenario modelling plots, we now show include
the plotting code for the prevented infections correlation plot in the
documentation.

doc/how-to/scenario-modelling.rst

@@ -272,6 +272,12 @@ Finally, we can plot the :ref:`correlations between prevented infections and pat
 
 - The daily force of infection :math:`\beta = R_0 \cdot \gamma` is more strongly correlated with the impact of vaccination than with the impact of reducing transmission, because the impact of vaccination strongly depends on the number of infections that have occurred prior to the start of vaccination.
 
+.. admonition:: Function that plots rank correlations.
+   :class: dropdown seealso
+
+   .. literalinclude:: ../../tests/test_sirv.py
+      :pyobject: plot_prevented_infection_correlations
+
 .. _fig-prevented-corrs:
 .. figure:: scenario-sirv-correlations.png
    :width: 100%