initSelection
  Deprecated in Select2 4.0. This has been replaced by another option and is only available in the full builds of Select2.
    In the past, Select2 required an option called initSelection
    that was defined whenever a custom data source was being used, allowing
    for the initial selection for the component to be determined. This has
    been replaced by the current method on the
    data adapter.
  
initSelection
        callback
        DataAdapter
        InitSelection