<plot function> (arg 1 , arg 2 , arg 3 , ...) clear3 ( )
When one of the plotting functions (plwf, pl3surf, pl3tree) is called and the internal variable
_draw3 has been set to zero, or else if it is nonzero and the idler is a do-nothing routine, Then this
plot call will add <plot function> to the display list, and will process the arguments into a
Python list, which will be added to the display list after the function name.
The function clear3 clears the display list of all plotting functions. It leaves orientation and lighting information unchanged.