code: public static PrivateDataProvider getPrivateDataProvider(String elementName, String namespace) {
          String key = XmppStringUtils.generateKey(elementName, namespace);
          return privateDataProviders.get(key);
      }
docs: Returns the private data provider registered to the specified XML element name and namespace.
  For example, if a provider was registered to the element name "prefs" and the
  namespace "http://www.xmppclient.com/prefs", then the following stanza would trigger
  the provider:
  
  <pre>
  &lt;iq type='result' to='joe@example.com' from='mary@example.com' id='time_1'&gt;
  &lt;query xmlns='jabber:iq:private'&gt;
  &lt;prefs xmlns='http://www.xmppclient.com/prefs'&gt;
  &lt;value1&gt;ABC&lt;/value1&gt;
  &lt;value2&gt;XYZ&lt;/value2&gt;
  &lt;/prefs&gt;
  &lt;/query&gt;
  &lt;/iq&gt;</pre>
  
  <p>Note: this method is generally only called by the internal Smack classes.
  
  @param elementName the XML element name.
  @param namespace the XML namespace.
  @return the PrivateData provider.