dita-ot: PDF table of content does not show section numbers when using dita "

Expected Behavior

PDF toc should show section numbers of the topics rendered with the topic number.

Contents
1. Introduction...................................................................... 4
1.1 Block diagram colors........................................................4

Actual Behavior

Contents
Introduction...................................................................... 4
Block diagram colors........................................................4

Steps to Reproduce

Grab Dita version 3.1.2, add topics “Introduction” and “Block diagram colors” where the second one is a child of the first

Environment

• DITA-OT version: 3.1.2

• Operating system and version: Linux

• How did you run DITA-OT? dita command

• Transformation type: PDF