update example sections

Author: SvenKlaassen

doc/api/api.rst

@@ -1,3 +1,5 @@
+.. _python_api:
+
 API reference
 =============
 

doc/examples/index.rst

@@ -6,24 +6,24 @@
 Examples
 ==========
 
-|start-h3| R: Case studies |end-h3|
+R: Case studies
+---------------
 
 These are case studies with the R package :ref:`DoubleML <doubleml_package>`.
 
 .. nbgallery::
     :name: case-studies-r
-    :glob:
 
     R_double_ml_pension.ipynb
     r_double_ml_multiway_cluster.ipynb
 
-|start-h3| Python: Case studies |end-h3|
+Python: Case studies
+---------------------
 
 These are case studies with the Python package :ref:`DoubleML <doubleml_package>`.
 
 .. nbgallery::
     :name: case-studies-py
-    :glob:
 
     py_double_ml_pension.ipynb
     py_double_ml_multiway_cluster.ipynb
@@ -36,22 +36,14 @@ These are case studies with the Python package :ref:`DoubleML <doubleml_package>
     py_double_ml_cvar.ipynb
     py_double_ml_learner.ipynb
 
-|start-h3| Sandbox |end-h3|
+Sandbox
+-----
 
 These are examples which are work-in-progress and/or not yet fully documented.
 
 .. nbgallery::
-    :name: sandbox
-    :glob:
+    :name: sandbox_gallery
     :maxdepth: 1
 
     R_double_ml_pipeline.ipynb
     double_ml_bonus_data.ipynb
-
-.. |start-h3| raw:: html
-
-     <h3>
-
-.. |end-h3| raw:: html
-
-     </h3>