Added example for region boundary merging

doc/examples/segmentation/plot_rag.py

@@ -23,29 +23,30 @@ import numpy as np
 def max_edge(g, src, dst, n):
     """Callback to handle merging nodes by choosing maximum weight.
 
-    Returns either the weight between (`src`, `n`) or (`dst`, `n`)
-    in `g` or the maximum of the two when both exist.
+    Returns a dictionary with `"weight"` set as either the weight between
+    (`src`, `n`) or (`dst`, `n`) in `graph` or the maximum of the two when
+    both exist.
 
     Parameters
     ----------
-    g : RAG
+    graph : RAG
         The graph under consideration.
     src, dst : int
-        The vertices in `g` to be merged.
+        The verices in `graph` to be merged.
     n : int
         A neighbor of `src` or `dst` or both.
 
     Returns
     -------
-    weight : float
-        The weight between (`src`, `n`) or (`dst`, `n`) in `g` or the
-        maximum of the two when both exist.
-
+    data : dict
+        A dict with the `"weight"` attribute set the weight between
+        (`src`, `n`) or (`dst`, `n`) in `graph` or the maximum of the two when
+        both exist.
     """
 
     w1 = g[n].get(src, {'weight': -np.inf})['weight']
     w2 = g[n].get(dst, {'weight': -np.inf})['weight']
-    return max(w1, w2)
+    return {'weight': max(w1, w2)}
 
 
 def display(g, title):