Points to remember:
* XML must have a root element.
* XML only allows one root element
* To avoid multiple root issues, you must create a root element for the XML output, whenever we transform output
* When mapping array elements (JSON or JAVA) to XML, wrap the map operations in {(..)}
-{ } are defining the object
( ) are transforming each element in the array as a key/value pair
* The transformation to XML would fail if the above mentioned considerations were not taken into account.
* Thus the transformation script declares a root element as trains and wraps the data in “{( )}“.
Whenever you see such type of question, always look out for root element followed by {( )} wrapping map.
I call this a "Wrap The Map" scenario. Hope it would help you remember !