doc update (#1077)

* doc update

* fixes

Author: sahithyaravi

doc/usage.rst

@@ -76,9 +76,9 @@ Docker
 
 It is also possible to try out the latest development version of ``openml-python`` with docker:
 
-```
-    docker run -it openml/openml-python
-```
+
+    ``docker run -it openml/openml-python``
+
 
 
 See the `openml-python docker documentation <https://github.com/openml/openml-python/blob/main/docker/readme.md>`_ for more information.

openml/extensions/sklearn/extension.py

@@ -65,7 +65,10 @@
 
 
 class SklearnExtension(Extension):
-    """Connect scikit-learn to OpenML-Python."""
+    """Connect scikit-learn to OpenML-Python.
+       The estimators which use this extension must be scikit-learn compatible,
+       i.e needs to be a subclass of sklearn.base.BaseEstimator".
+    """
 
     ################################################################################################
     # General setup