What DataWeave expressiontransforms the array a to the XML output?

1.1. trains:2.2. {(3.3. a map ((engId, index) ->4.4. train: {5.5. TrainNumber: engId6.6.7.7. }8.8. )9.9. )}

1.1. trains:2.2. a map ((engId, index) ->3.3. train: {4.4. TrainNumber:engId5.5.6.6. }7.7. )

1.1. {(2.2. trains:3.3. a map ((engId, index) ->4.4. train: {5.5. TrainNumber: engId6.6.7.7. }8.8. )9.)}

1.1. {2.2. trains:3.3. a map ((engId, index) ->4.4. train: {5.5. TrainNumber: engId6.6.7.7. }8.8. )9.}