All such functions in the api seem to be use the spelling Linetype (with lower-case t) while every function call in the test code does use LineType instead.

Report is for version 3.7.5 as it was the only version I found to download on the qcad.org webpage.
Sourceforge also didn't seem to have any downloads and while I found a few dxflib clones on GitHub, none seemed official or up-to-date.
But maybe I'm just blind :-)