In order to define a contextual action for GIS layers, you need to put your Python script in your Python directory under a directory called Contextual_Map_Gis_Layer.
Go to Tools->Options->Environment->Python Scripts (or Tools->Options->Python->Scripts in INTViewer 5.2) and click "Refresh from Disk". Your script should be listed automatically.
You will now be able to execute this script from the contextual menu of the GIS layer:
This script will cycle through line styles if the GIS shape is made up of lines, symbol styles if the GIS shape is made up of points or fill styles if the
GIS shape is made up of closed shapes (as shown on this page).
This script is attached to the bottom of this article.
The result after the script executes should look something like the following.