| SAXONICA | 
The extension functions saxon:index() and saxon:find() have been changed.
            These functions allow creation of a user-defined index over a sequence, and fast retrieval of items from the sequence
            by using the index. The function saxon:index() no longer returns the sequence in question, rather
            it now defines an object of type {http://saxon.sf.net/java-type}com.saxonica.extra.IndexedSequence
            which can be used only as input to the saxon:find() function. The saxon:find()
            function now has a one-argument version which returns the sequence in question. This change has been made for
            robsustness: the existing design was proving excessively difficult to maintain.