Refactoring: prediction_builder knows its environment and can access the distance map directly

docs/intro_observationbuilder.rst

@@ -205,7 +205,7 @@ In contrast to the previous examples we also implement the :code:`def get_many(s
             :return:
             '''
 
-            self.predictions = self.predictor.get(custom_args={'distance_map': self.env.distance_map})
+            self.predictions = self.predictor.get()
 
             self.predicted_pos = {}
             for t in range(len(self.predictions[0])):

flatland/envs/observations.py

@@ -71,7 +71,7 @@ class TreeObsForRailEnv(ObservationBuilder):
             self.max_prediction_depth = 0
             self.predicted_pos = {}
             self.predicted_dir = {}
-            self.predictions = self.predictor.get(custom_args={'distance_map': self.env.distance_map})
+            self.predictions = self.predictor.get()
             if self.predictions:
 
                 for t in range(len(self.predictions[0])):