Resolve "thrill GA talk"

examples/real_lens_group.rs

+use opossum::error::OpossumError;
+use opossum::nodes::{Dummy, NodeGroup};
+use opossum::OpticScenery;
+use std::path::Path;
+
+fn main() -> Result<(), OpossumError> {
+    let mut scenery = OpticScenery::new();
+
+    let mut group1 = NodeGroup::new("real lens group");
+    group1.expand_view(true);
+    let g1_n1 = group1.add_node(Dummy::new("surface"))?;
+    let g1_n2 = group1.add_node(Dummy::new("material propagation"))?;
+    let g1_n3 = group1.add_node(Dummy::new("surface"))?;
+    group1.connect_nodes(g1_n1, "rear", g1_n2, "front")?;
+    group1.connect_nodes(g1_n2, "rear", g1_n3, "front")?;
+
+    let _scene_g1 = scenery.add_node(group1);
+    scenery.save_to_file(Path::new("playground/real_lens_group.opm"))?;
+    Ok(())
+}

examples/simple_for_talk.rs

+use opossum::error::OpossumError;
+use opossum::nodes::{Dummy, Source, EnergyMeter};
+use opossum::OpticScenery;
+use std::path::Path;
+
+fn main() -> Result<(), OpossumError> {
+    let mut scenery = OpticScenery::new();
+    scenery.set_description("OpticScenery demo");
+    let node1 = scenery.add_node(Source::default());
+    let node2 = scenery.add_node(Dummy::new("optic"));
+    let node3 = scenery.add_node(EnergyMeter::default());
+    scenery.connect_nodes(node1, "out1", node2, "front")?;
+    scenery.connect_nodes(node2, "rear", node3, "in1")?;
+    scenery.save_to_file(Path::new("playground/simple_for_talk.opm"))?;
+    Ok(())
+}

src/main.rs

@@ -36,7 +36,7 @@ fn do_it() -> OpmResult<()> {
     dot_path.set_extension("dot");
     print!("Write diagram to {}...", dot_path.display());
     let mut output = File::create(dot_path).unwrap();
-    write!(output, "{}", scenery.to_dot("")?).unwrap();
+    write!(output, "{}", scenery.to_dot("LR")?).unwrap();
     println!("Success");
     print!("\nAnalyzing...");
     scenery.analyze(&opossum_args.analyzer)?;