Select and activate input method INPUT-METHOD for the current buffer.
This also sets the default input method to the one you specify.
If INPUT-METHOD is nil, this function turns off the input method, and
also causes you to be prompted for a name of an input method the next
time you invoke C-\.
When called interactively, the optional arg INTERACTIVE is non-nil,
which marks the variable `default-input-method' as set for Custom buffers.
To deactivate the input method interactively, use C-\.
To deactivate it programmatically, use `deactivate-input-method'.