instruction - gives information about the instruction being
executed, and about the context in which it is executed. This object is mutable,
so if information from the InstructionInfo is to be retained, it must be copied.
instruction - gives the same information that was supplied to the
enter method, though it is not necessarily the same object. Note that the
line number of the instruction is that of the start tag in the source stylesheet,
not the line number of the end tag.
Method that is called by an instruction that changes the current item
in the source document: that is, xsl:for-each, xsl:apply-templates, xsl:for-each-group.
The method is called after the enter method for the relevant instruction, and is called
once for each item processed.
Method that is called when an instruction has finished processing a new current item
and is ready to select a new current item or revert to the previous current item.
The method will be called before the leave() method for the instruction that made this
currentItem - the item that was current, whose processing is now complete. This will represent
the same underlying item as the corresponding startCurrentItem() call, though it will
not necessarily be the same actual object.