Update tutorials/intro.md

Co-authored-by: Jeremy Paige <[email protected]>

tutorials/intro.md

@@ -270,7 +270,7 @@ this consistency throughout your entire package. [Learn more about code formatte
 
 **Documented code:** documented code is written using docstrings that help a
 user understand both what the functions and methods in your code do and also
-what the input and output elements of each function is. [You can learn more about docstrings in our guide, here.](../documentation/write-user-documentation/document-your-code-api-docstrings)
+what the input and output elements of each function are. [You can learn more about docstrings in our guide, here.](../documentation/write-user-documentation/document-your-code-api-docstrings)
 
 ## Making your package installable - publishing to PyPI & conda-forge