Fix rcf default batch_size

Author: Dan Choi

src/sagemaker/amazon/randomcutforest.py

@@ -87,10 +87,12 @@ def create_model(self):
 
         return RandomCutForestModel(self.model_data, self.role, sagemaker_session=self.sagemaker_session)
 
-    def _prepare_for_training(self, records, mini_batch_size=MINI_BATCH_SIZE, job_name=None):
-        if mini_batch_size != self.MINI_BATCH_SIZE:
-            raise ValueError("Random Cut Forest uses a fixed mini_batch_size of {}"
-                             .format(self.MINI_BATCH_SIZE))
+    def _prepare_for_training(self, records, mini_batch_size=None, job_name=None):
+        if mini_batch_size is None:
+            mini_batch_size = self.MINI_BATCH_SIZE
+        elif mini_batch_size != self.MINI_BATCH_SIZE:
+            raise ValueError("Random Cut Forest uses a fixed mini_batch_size of {}".format(self.MINI_BATCH_SIZE))
+
         super(RandomCutForest, self)._prepare_for_training(records, mini_batch_size=mini_batch_size, job_name=job_name)