serializer.setProperty("http://xmlpull.org/v1/doc/properties.html#serializer-line-separator", "\n");
        serializer.setOutput(stream, coreExtensions.getModelEncoding());
        serializer.startDocument(coreExtensions.getModelEncoding(), null);
        writeCoreExtensions(coreExtensions, "extensions", serializer);
        serializer.endDocument();
    } // -- void write( OutputStream, CoreExtensions )

    /**

    } // -- List<CoreExtension> getExtensions()

    /**
     * Get the modelEncoding field.
     *
     * @return String
     */
    public String getModelEncoding() {
        return this.modelEncoding;
    } // -- String getModelEncoding()

    /**
     * Method removeExtension.
     *
     * @param coreExtension a coreExtension object.
     */
    public void removeExtension(CoreExtension coreExtension) {

        Objects.requireNonNull(output, "output cannot be null");
        Objects.requireNonNull(model, "model cannot be null");

        String encoding = model.getModelEncoding();
        // TODO Use StringUtils here
        if (encoding == null || encoding.length() <= 0) {
            encoding = "UTF-8";
        }

        try (Writer out = new OutputStreamWriter(output, encoding)) {