private Map<ShapeId, ShapeId> getShapeIdsToRename(Config config, Model model) {
        Map<ShapeId, ShapeId> shapeIdMap = new HashMap<>();
        for (String fromShape : config.getRenamed().keySet()) {
            ShapeId fromShapeId = getShapeIdFromString(fromShape);
            if (!model.getShape(fromShapeId.toShapeId()).isPresent()) {
                throw new SmithyBuildException(
                        String.format("'%s' to be renamed does not exist in model.", fromShapeId));
            }
            shapeIdMap.put(fromShapeId, getShapeIdFromString(config.getRenamed().get(fromShape)));
        }
        return shapeIdMap;
    }
Gets the map of shape ids to be renamed.

@return The map of shapes to rename.
smithy-build/src/main/java/software/amazon/smithy/build/transforms/RenameShapes.java