Add sentinel_helpers.py

_config.yml

@@ -12,4 +12,11 @@ logo: great-forty-foot-telescope-wikipedia.png  # A path to the book logo
 execute:
   execute_notebooks: "off"
 
+sphinx:
+  config:
+    nb_custom_formats:
+      .py:
+        - jupytext.reads
+        - fmt: Rmd
+ 
 exclude_patterns: [_build, .cache, .config, .local, .npm, Thumbs.db, .DS_Store, "**.ipynb_checkpoints"]

_toc.yml

@@ -26,3 +26,6 @@
   - file: "sources/03b Example Initialized Downloads.ipynb"
   - file: "sources/03b Forest Fires 2018 and 2019.ipynb"
   - file: "sources/03c dNBR.ipynb"
+- part: "Appendix"
+  chapters:
+  - file: "sources/sentinel_helpers.py"