public Optional<Integer> getLine() {
        return Optional.ofNullable(line);
    }
Gets this ShapeLink's line number in an optional container.
Line is the line number in the file that contains the artifact component.

@return Optional container holding this ShapeLink's line number
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/trace/ShapeLink.java