ci precommit

Author: AnandMukherjee2004

doc/source/getting_started/intro_tutorials/03_subset_data.rst

@@ -54,6 +54,8 @@ I’m interested in the age of the Titanic passengers.
 To select a single column, use square brackets ``[]`` with the column
 name of the column of interest.
 
+For more explanation, see `Brackets in Python and pandas <https://python-public-policy.afeld.me/en/columbia/brackets.html>`__.
+
 .. raw:: html
 
         </li>