private void writeDocumentType(DocumentType docType, Writer writer, int depth) throws IOException {
        String publicId = docType.getPublicId();
        String internalSubset = docType.getInternalSubset();

        for (int i = 0; i < depth; ++i) { writer.append(' '); }
        writer.append("<!DOCTYPE ").append(docType.getName());
        if (publicId != null) {
            writer.append(" PUBLIC '").append(publicId).append("' ");
        } else {
            writer.write(" SYSTEM ");
        }
        writer.append("'").append(docType.getSystemId()).append("'");
        if (internalSubset != null) {
            writer.append(" [").append(internalSubset).append("]");
        }
        writer.append('>').append(lineSeparator);
    }
Set the line separator that will be used when serializing documents.
<p>
If this is not called then the serializer uses a default based on the
{@code line.separator} system property. 

@param lineSeparator the line separator to set.
jme3-plugins/src/xml/java/com/jme3/export/xml/DOMSerializer.java