The `signature()` getter can just return a reference to the private vector
member variable, and let the caller make a copy if needed. Since the
return type is const qualified, this was likely the original intention.
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>