degrade logging message in prepare batches to debug, /close #350

mlair/data_handler/iterator.py

@@ -143,7 +143,7 @@ class KerasIterator(keras.utils.Sequence):
         remaining = None
         mod_rank = self._get_model_rank()
         for data in self._collection:
-            logging.info(f"prepare batches for {str(data)}")
+            logging.debug(f"prepare batches for {str(data)}")
             X = data.get_X(upsampling=self.upsampling)
             Y = [data.get_Y(upsampling=self.upsampling)[0] for _ in range(mod_rank)]
             if self.upsampling: