public synchronized String getPrivateChunkType(int index) {
        return (String)chunkType.get(index);
    }
Returns the type of the private chunk at a given index, as a
4-character <code>String</code>.  The index must be smaller
than the return value of <code>getNumPrivateChunks</code>.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/png/PNGEncodeParam.java