Currently, there are two types of backends for lepton-netlist:
Initially, legacy backend system had been inherited from gEDA
gnetlist, and since its invention, file names of legacy
backends had to have, and must now have, the prefix gnet-. As
both types of backends are Scheme files, they should have the
extension .scm. A backend of any type should define a main
function named the same as the backend itself. Please note that the
name of a backend is not the same as of its file name. Subtle
differences in naming will be revealed in the next sections.
In both cases lepton-netlist loads and evaluates the main backend function
at a certain stage of its execution.