public BuildParameterBuilder addSourcesIfExists(Collection<String> sources) {
        if (sources != null) {
            for (String source : sources) {
                if (!source.isEmpty() && Files.exists(Paths.get(source))) {
                    this.sources.add(source);
                } else {
                    LOGGER.info("Skipping source that does not exist: " + source);
                }
            }
        }

        return this;
    }
Adds a collection of "source" model files only if they exist.

@param sources Sources to add.
@return Returns the builder.
smithy-cli/src/main/java/software/amazon/smithy/cli/BuildParameterBuilder.java