public Reader getReader() {
            if (zipEntry == null) {
                return new StringReader("");
            }
            try {
                return new InputStreamReader(bundle.jarFile.getInputStream(zipEntry), StandardCharsets.UTF_8);
            }  catch (IOException e) {
                throw new IllegalArgumentException("IOException", e);
            }
        }
Returns the namespace of the .def-file, as given by the "namespace=" statement inside the given entry.
@return  The namespace string, or "" (empty string) if no namespace exists
config-application-package/src/main/java/com/yahoo/config/model/application/provider/Bundle.java