method
insert_before
insert_before( child1, child2 )
public
Inserts an child before another child @param child1 this is either an xpath or an Element. If an Element, child2 will be inserted before child1 in the child list of the parent. If an xpath, child2 will be inserted before the first child to match the xpath. @param child2 the child to insert @return the parent (self)