postinst is in python-sqlite-dbg 1.0.1-12.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10  | #!/bin/sh
set -eu
if dpkg-maintscript-helper supports symlink_to_dir; then
    dpkg-maintscript-helper \
        symlink_to_dir \
        /usr/share/doc/python-sqlite-dbg /usr/share/doc/python-sqlite \
        1.0.1-9 python-sqlite-dbg -- "$@"
fi
 |