|  | 
|  |  |  |  | 
This function returns the value true if and only if the data object reference specifies the variant of the union type that is actually selected for a given data object.
Related keyword:
| ischosen(any_type value) return boolean | 
Example 1:
   type union MyUnion ...
   // and given that MyPDU is a template of MyUnion type
     {  PDU_type1 p1,
        PDU_type2 p2,
        PDU_type p3
     }
  // and received_PDU is also of MyUnion type 
  // then 
  MyPort.receive(MyPDU) -> value received_PDU
  ischosen(received_PDU.p2)
  // returns true if the actual instance of MyPDU carries a PDU of the type PDU_type2