def write_marker(marker = nil) # :nodoc:
      marker ||= @default_marker

      return unless ptrue?(marker)
      return if ptrue?(marker.automatic?)

      @writer.tag_elements('c:marker') do
        # Write the c:symbol element.
        write_symbol(marker.type)
        # Write the c:size element.
        size = marker.size
        write_marker_size(size) if ptrue?(size)
        # Write the c:spPr element.
        write_sp_pr(marker)
      end
    end
def write_marker(marker = nil) # :nodoc:
      marker ||= @default_marker

      return unless ptrue?(marker)
      return if ptrue?(marker.automatic?)

      @writer.tag_elements('c:marker') do
        # Write the c:symbol element.
        write_symbol(marker.type)
        # Write the c:size element.
        size = marker.size
        write_marker_size(size) if ptrue?(size)
        # Write the c:spPr element.
        write_sp_pr(marker)
      end
    end
Write the <c:marker> element.