Do not make trajectory an internal property

No need for this property to be internal.

trajectories.py

@@ -3,7 +3,7 @@
 """A script that loads a segmented cf graph in the gt format, iterates
 on all of the edges and cost functions and generates the trajectories
 as done in MATLAB. Segments (nodes) have a new vertex property called
-"traj" that holds the trajectory ID that that segment belongs to. The
+"traj_prop" that holds the trajectory ID that that segment belongs to. The
 output is either an expanded JSON file and/or an edgelist file with
 all of the trajectories.
 
@@ -26,17 +26,17 @@ class Visitor(search.BFSVisitor):
         self.trajectories = {}
 
     def discover_vertex(self, u):
-        if g.vp.traj[u] not in self.trajectories:
-            self.trajectories[g.vp.traj[u]] = [g.vp.name[u]]
+        if traj_prop[u] not in self.trajectories:
+            self.trajectories[traj_prop[u]] = [g.vp.name[u]]
         else:
-            self.trajectories[g.vp.traj[u]].append(g.vp.name[u])
+            self.trajectories[traj_prop[u]].append(g.vp.name[u])
 
 g = graph_tool.load_graph(sys.argv[1])
-g.vp['traj'] = g.new_vp('int')
+traj_prop = g.new_vp('int')
 
 # Assign the new vertex property:
 for node in g.vertices():
-    g.vp.traj[node] = g.vp.name[node]
+    traj_prop[node] = g.vp.name[node]
 
 print('Setting trajectory vertex property...')
 
@@ -52,17 +52,17 @@ for edge in g.edges():
                 if current_cf <= min({g.ep.cost_function[e]
                                       for e in trg.out_edges()}):
                     # Set trg trajectory to src trajectory
-                    g.vp.traj[trg] = g.vp.traj[src]
+                    traj_prop[trg] = traj_prop[src]
             else:
-                g.vp.traj[trg] = g.vp.traj[src]
+                traj_prop[trg] = traj_prop[src]
     else:
         # src.out_degree() == 1
         if trg.in_degree() > 1:
             if current_cf <= min({g.ep.cost_function[e]
                                   for e in trg.in_edges()}):
-                g.vp.traj[trg] = g.vp.traj[src]
+                traj_prop[trg] = traj_prop[src]
         else:
-            g.vp.traj[trg] = g.vp.traj[src]
+            traj_prop[trg] = traj_prop[src]
 
 print('Creating the dictionary of trajectories...')
 visitor = Visitor()