do not force mlflow

dan/ocr/document/train.py

@@ -28,6 +28,14 @@ try:
 except ImportError:
     MLFLOW = False
 
+try:
+    import mlflow
+
+    MLFLOW = True
+    logger.info("MLflow Logging available.")
+except ImportError:
+    MLFLOW = False
+
 logger = logging.getLogger(__name__)