add fill_value default value to docstring
@@ -118,7 +118,7 @@ class SimpleImputer(BaseEstimator, TransformerMixin):
.. versionadded:: 0.20
strategy="constant" for fixed value imputation.
- fill_value : string or numerical value, optional
+ fill_value : string or numerical value, optional (default=None)
When strategy == "constant", fill_value is used to replace all
occurrences of missing_values.
If left to the default, fill_value will be 0 when imputing numerical
