+ subexpressions = list(elt)
+ if len(subexpressions) > 0:
+ # sumof with a nested expression which is to be evaluated
+ # for each list-element in the context of that list-element.
+ # sumof then returns the sum of the results of these evaluations
+ self.rhs = Expression(subexpressions[0], parent)
+
+ elif elt.tag == 'listelement-ref':
+ # current list element inside iterating expressions such as sumof
+ self.op = 'listelement-ref'
+ self.contains_listelement_ref = True