Of course, look at the source code:
M-x find-library RET isearch RET
C-s mode-map
This is probably more reliable, because people may not name their layouts, as you might expect, and in some modes there is more than one keyboard layout (which leads to the fact that your search may not be found). A good example of the need to view code is 'viper-modethat has several different layouts that are active in different situations.
. , find-library find-function.