lookup-nested-alist
    
    lookup-nested-alist is an autoloaded compiled Lisp function in `mule-util.el'.
(lookup-nested-alist KEYSEQ ALIST &optional LEN START NIL-FOR-TOO-LONG)
Look up key sequence KEYSEQ in nested alist ALIST.  Return the definition.
Optional 3rd argument LEN specifies the length of KEYSEQ.
Optional 4th argument START specifies index of the starting key.
The returned value is normally a nested alist of which
car part is the entry for KEYSEQ.
If ALIST is not deep enough for KEYSEQ, return number which is
 how many key elements at the front of KEYSEQ it takes
 to reach a leaf in ALIST.
Optional 5th argument NIL-FOR-TOO-LONG non-nil means return nil
 even if ALIST is not deep enough.