read-input-method-name
read-input-method-name is a compiled Lisp function in `mule-cmds.el
'.
(read-input-method-name PROMPT &optional DEFAULT INHIBIT-NULL)
Read a name of input method from a minibuffer prompting with PROMPT.
If DEFAULT is non-nil, use that as the default,
and substitute it into PROMPT at the first `%s'.
If INHIBIT-NULL is non-nil, null input signals an error.
The return value is a string.