PacketExtension
===============
The static `from(Stanza)` Method
--------------------------------
Every PacketExtension class must have a static `from()` method that retrieves that extension for a given Stanza (if any).
Sample Code
```java
public static RSMSet from(Stanza) {
return packet.getExtension(ELEMENT, NAMESPACE);
}
```
Sometimes certain PacketExtension's are only found in one stanza type, in that case, specify the parameter type. For example `public static CarbonExtension getFrom(Message)`.
