Set<ClassLoader> getExternalClassLoaders() {
    Set<ClassLoader> externalClassLoaders = new HashSet<>();
    final ClassLoader systemClassLoader = this.getClass().getClassLoader();
    for (E env : coprocEnvironments) {
      ClassLoader cl = env.getInstance().getClass().getClassLoader();
      if (cl != systemClassLoader) {
        // do not include system classloader
        externalClassLoaders.add(cl);
      }
    }
    return externalClassLoaders;
  }
Retrieves the set of classloaders used to instantiate Coprocessor classes defined in external
jar files.
@return A set of ClassLoader instances
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/CoprocessorHost.java