def initialize(frame, options={})
      @vary_colors = false
      @grouping = :standard
      super(frame, options)
      @series_type = AreaSeries
      @d_lbls = nil
    end
Creates a new line chart object
@param [GraphicFrame] frame The workbook that owns this chart.
@option options [Cell, String] title
@option options [Boolean] show_legend
@option options [Symbol] grouping
@see Chart