docs: public static EsaSubsystemFeatureDefinitionImpl constructInstance(File esa) throws ZipException, IOException {
          // Find the manifest - case isn't guaranteed so do a search
          ZipFile zip = new ZipFile(esa);
          Enumeration<? extends ZipEntry> zipEntries = zip.entries();
          ZipEntry subsystemEntry = null;
          while (zipEntries.hasMoreElements()) {
              ZipEntry nextEntry = zipEntries.nextElement();
              if ("OSGI-INF/SUBSYSTEM.MF".equalsIgnoreCase(nextEntry.getName())) {
                  subsystemEntry = nextEntry;
              }
          }
          return new EsaSubsystemFeatureDefinitionImpl(zip.getInputStream(subsystemEntry), zip);
      }