fix write_friend_tree

toolkit.py

@@ -887,9 +887,9 @@ class ClassificationProject(object):
             logger.info("Evaluating score for entry {}/{}".format(start, entries))
             logger.debug("Loading next batch")
             x_from_tree = tree2array(tree,
-                                     branches=self.fields+self.identifiers,
+                                     branches=self.branches+self.identifiers,
                                      start=start, stop=start+batch_size)
-            x_eval = rec2array(x_from_tree[self.fields])
+            x_eval = rec2array(x_from_tree[self.branches])
 
             if len(self.identifiers) > 0:
                 # create list of booleans that indicate which events where used for training