public Optional<String> getFile() {
        return Optional.ofNullable(file);
    }
Gets this ShapeLink's file in an optional container.
File is a URI that defines the location of the artifact component. Files MUST use the "file" URI scheme,
and SHOULD be relative.

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