This interface is implemented by all XSL elements that can contain local variable declarations.
Specifically, a top-level xsl:template, xsl:variable, xsl:param, or xsl:function element
or an xsl:attribute-set element or xsl:key element.
Get the SlotManager associated with this stylesheet construct. The SlotManager contains the
information needed to manage the local stack frames used by run-time instances of the code.