private boolean hasOutput(Picture picture) {
            return output.contains(picture);
        }
Provides access to the pictures both by offset, iteration
over the un-claimed, and peeking forward
<p>
TODO When POI 3.18 is out, replace this with PictureRunMapper,
which is this class ported over into POI core
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-microsoft-module/src/main/java/org/apache/tika/parser/microsoft/WordExtractor.java