code: public ExtensionElement removeExtension(String elementName, String namespace) {
          String key = XmppStringUtils.generateKey(elementName, namespace);
          synchronized (packetExtensions) {
              return packetExtensions.remove(key);
          }
      }
docs: Remove the stanza extension with the given elementName and namespace.
  
  @param elementName
  @param namespace
  @return the removed stanza extension or null.