FIX: passing non default params for default models STLTransform

CHANGELOG.md

@@ -29,7 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 -
 
 ### Fixed
--
+- Passing non default params for default models STLTransform ([#641](https://github.com/tinkoff-ai/etna/pull/641))
 - 
 - Fixed bug in models `get_model` method ([#623](https://github.com/tinkoff-ai/etna/pull/623))
 - Fixed unsafe comparison in plots ([#611](https://github.com/tinkoff-ai/etna/pull/611))

etna/transforms/decomposition/stl.py

@@ -58,10 +58,12 @@ def __init__(
         if isinstance(model, str):
             if model == "arima":
                 self.model = ARIMA
-                model_kwargs = {"order": (1, 1, 0)}
+                if len(model_kwargs) == 0:
+                    model_kwargs = {"order": (1, 1, 0)}
             elif model == "holt":
                 self.model = ETSModel
-                model_kwargs = {"trend": "add"}
+                if len(model_kwargs) == 0:
+                    model_kwargs = {"trend": "add"}
             else:
                 raise ValueError(f"Not a valid option for model: {model}")
         elif isinstance(model, TimeSeriesModel):