def to_xml_string(str = '')
      str << '<sheetViews>'
      str << '<sheetView '
      serialized_attributes str
      str << '>'
      @pane.to_xml_string(str) if @pane
      @selections.each do |key, selection|
        selection.to_xml_string(str)
      end
      str << '</sheetView>'
      str << '</sheetViews>'
    end
def to_xml_string(str = '')
      str << '<sheetViews>'
      str << '<sheetView '
      serialized_attributes str
      str << '>'
      @pane.to_xml_string(str) if @pane
      @selections.each do |key, selection|
        selection.to_xml_string(str)
      end
      str << '</sheetView>'
      str << '</sheetViews>'
    end
Serializes the data validation
 @param [String] str
 @return [String]