skrat/blender-pycollada — comment on commit 39e3b26076b9e4028c49c59e5ffa591f555216e1
File: import_collada.py line 141
By skrat:

This seem to be SketchUp specific way of handling textures. COLLADA uses `transparent` & `transparency` elements for these textures. We can subclass `ColladaImport` and override `import_rendering_diffuse`.