Add property set_input to variable interface

packages/lib/src/variables.ts

@@ -65,6 +65,7 @@ export interface Variable {
   possible_values?: { [name: string]: string }
   reference?: ReferencesByInstant
   referring_variables?: string[]
+  set_input?: string
   start_line_number: number
   stop_line_number: number
   /// Unit added by customizations or decompositions