python: highlighting functions for edges and states

* python/spot/impl.i (highlight_state, highlight_edge): New function.
* python/spot/__init__.py (highlight_states, highlight_edges): New
functions.
* spot/twaalgos/dot.cc: Add a '#' option.
* spot/taalgos/dot.cc: Ignore '#'.
* tests/python/highlighting.ipynb: New file to illustrate everything.
* tests/Makefile.am, doc/org/tut.org: Add it.

python/spot/__init__.py

@@ -147,6 +147,15 @@ class twa:
         from IPython.display import SVG
         return SVG(self._repr_svg_(opt))
 
+    def highlight_states(self, states, color):
+        for state in states:
+            self.highlight_state(state, color)
+        return self
+
+    def highlight_edges(self, edges, color):
+        for edge in edges:
+            self.highlight_edge(edge, color)
+        return self
 
 @_extend(twa)
 class twa:

python/spot/impl.i

@@ -546,6 +546,32 @@ namespace std {
   {
     return self->get_named_prop<std::vector<std::string>>("state-names");
   }
+
+  twa* highlight_state(unsigned state, unsigned color)
+  {
+    auto hs =
+      self->get_named_prop<std::map<unsigned, unsigned>>("highlight-states");
+    if (!hs)
+      {
+	hs = new std::map<unsigned, unsigned>;
+	self->set_named_prop("highlight-states", hs);
+      }
+    (*hs)[state] = color;
+    return self;
+  }
+
+  twa* highlight_edge(unsigned edge, unsigned color)
+  {
+    auto ht =
+      self->get_named_prop<std::map<unsigned, unsigned>>("highlight-edges");
+    if (!ht)
+      {
+	ht = new std::map<unsigned, unsigned>;
+	self->set_named_prop("highlight-edges", ht);
+      }
+    (*ht)[edge] = color;
+    return self;
+  }
 }