lgl_new()
instantiates a newlgl
node.lgl_type()
checks if the node is algl
node.lgl_<child>_get()
returns the<child>
node oflgl
.lgl_<child>_set()
sets the new<child>
and deletes the old<child>
.lgl_<child>_rep()
sets the new<child>
and returns the old<child>
.