[AUCTeX] How to set a style for a document explicitly?

[Guy Wiener]

Hello to Auctex group,
I am using auctex to edit some beamer files. However, because I use
several levels of \input, and the \documentclass declaration is in an
entirely different file, auctex does not recognize the document style as
"beamer".

Is there a way to explicitly set the style of a document? For example,
by using a local variable or a function call?

Thank you,
  Guy Wiener.