$$FilterValue Function
Syntax :
$$FilterValue : ValueExpression : CollectionName : PositionSpecifier : FilterExpression
Remarks:-
1) The $$FilterValue function allows you to apply a filter (FilterExpression) on a specified Collection (CollectionName), and
2) Get the first or the last Object (PositionSpecifier) of that filtered list and
3) Retrieve the value of any field/method (ValueExpression) of the first or last object as specified by PositionSpecifier.