If you’re looking for an Apress book’s source code, go to go directly to Github: https://github.com/Apress/ and search by the title/ISBN to locate the source code for the title.
Note: Many of the Apress titles list the actual Github URL for the book's source code within the book itself.
Missing Source Codes
Machine Learning with the Raspberry Pi by Donald J Norris. The author was unable to submit the source code for this book due to poor health.