how is "tiles.xpm" created?

Looking in the MicropolisCore folder of the sourcecode, the part of the Micropolis release project that is unfinished, trying to find an engine that generates the tiles.xpm image file.
Here is the listing of the content of the MicropolisCore folder

cities/
documentation/
images/
makefile
MicropolisCore
res/
src/

in the src/ there are two executable files to be found, here is a listing of this folder's content:

CellEngine/
cities/
Doxyfile
images/
__init__.py
makefile
MicropolisCore.sln
MicropolisCore-src
MicropolisEngine/
notes/
pyMicropolis/
res/
run-cell*
run-gtkfrontend*
TileEngine/

run-cell is actually a python script, containing the lines

#!/usr/bin/env python
#
from pyMicropolis.gtkFrontend import maincell
maincell.run()

that runs the maincell.run() function using the image file found at
src/images/tilesEngine/tiles.png








This still does not answer the question where the tiles.xpm is created.