def to_item
      item = DICOM::Item.new
      item.add(DICOM::Element.new(COLL_TYPE, @type))
      item.add(DICOM::Element.new(COLL_POS, positions_string))
      return item
    end
def to_item
      item = DICOM::Item.new
      item.add(DICOM::Element.new(COLL_TYPE, @type))
      item.add(DICOM::Element.new(COLL_POS, positions_string))
      return item
    end
Creates a Beam Limiting Device Position Sequence Item
 from the attributes of the CollimatorSetup.

 @return [DICOM::Item] the created DICOM item