OptionalstartThe point the line starts at, before the extension.
OptionalendThe point the line ends at, before the extension.
OptionalextensionHow far the line is lengthened past its start, in model units.
OptionalextensionHow far the line is lengthened past its end, in model units.
Two points and how far to lengthen the line past each for
shapes.wire.createLineWireWithExtensions.