code: public Tree clear() {
  		if (value != null) {
  			if (isMap()) {
  
  				((Map<?, ?>) value).clear();
  
  			} else if (value instanceof Collection) {
  
  				((Collection<?>) value).clear();
  
  			} else if (isArray()) {
  
  				setObjectInternal(new LinkedList<Object>());
  
  			} else {
  
  				setObjectInternal(null);
  
  			}
  		}
  		return this;
  	}
docs: Removes all of the sub-nodes from this node or sets the value to null.
  The node will be empty after this call returns. Sample code:<br>
  <br>
  node.clear().put("a", 1).put("b", 2);
  
  @return this (empty) node