webdoc: GISAS: resume explanation

hugo/content/py/simulation/gisas/no-dwba-terms/index.md

@@ -20,3 +20,9 @@ and therefore the DWBA boils down to the ordinary Born approximation.
 {{< /galleryscg >}}
 
 {{< highlightfile file="Examples/scatter2d/CylindersInBA.py" >}}
+
+### Explanation
+
+#### Function get_simulation
+
+The simulation of type `ScatteringSimulation` is defined by beam, sample, and detector.