private boolean hasUriBeenApplied(final String prefix, final String uri) {
        return appliedPrefixToUriMap.entrySet()
                .stream()
                .anyMatch(prefixToUriEntry ->
                        Objects.equals(prefixToUriEntry.getKey(), prefix)
                        && Objects.equals(prefixToUriEntry.getValue(), uri));
    }
@param ch     An array of characters.
@param start  The starting position in the array.
@param length The number of characters to use from the array.
@throws org.xml.sax.SAXException The client may throw an exception during processing.
@see stroom.pipeline.filter.AbstractXMLFilter#characters(char[],
int, int)
stroom-pipeline/src/main/java/stroom/pipeline/refdata/ReferenceDataFilter.java