To help answer this question, we can perform the following steps:
Load the flyspell.el library by typing M: aka M-x eval-expression, and then (require 'flyspell)
Locate the source code for the function flyspell-prog-mode by typing:
M-x find-function RET flyspell-prog-mode RET
Step two leads us to the source code of the function flyspell-prog-mode, which ...