Architecture behind CodeWhisperer

H, CW FAQ says

https://aws.amazon.com/codewhisperer/faqs/

How does Code Whisperer work?
As you are writing code, CodeWhisperer analyzes the English language comments
 and surrounding code to infer what code is needed to complete the task at hand. 
CodeWhisperer suggests one or more code snippets directly in the code editor, 
accelerating you as you code. The code suggestions provided by CodeWhisperer
are based on a large language models (LLMs) trained on billions of lines of code, 
including Amazon and open-source code. You can quickly and more easily accept 
the top suggestion (tab key), view more suggestions (arrow keys), or continue 
writing your own code. Always review a code suggestion before accepting it, 
and you may need to edit it to ensure that it does exactly what you intended.