def write_c_chart(id)
      schema  = 'http://schemas.openxmlformats.org/'
      xmlns_c = "#{schema}drawingml/2006/chart"
      xmlns_r = "#{schema}officeDocument/2006/relationships"


      attributes = [
                    ['xmlns:c', xmlns_c],
                    ['xmlns:r', xmlns_r]
                   ]
      attributes << r_id_attributes(id)

      @writer.empty_tag('c:chart', attributes)
    end
def write_c_chart(id)
      schema  = 'http://schemas.openxmlformats.org/'
      xmlns_c = "#{schema}drawingml/2006/chart"
      xmlns_r = "#{schema}officeDocument/2006/relationships"


      attributes = [
                    ['xmlns:c', xmlns_c],
                    ['xmlns:r', xmlns_r]
                   ]
      attributes << r_id_attributes(id)

      @writer.empty_tag('c:chart', attributes)
    end
Write the <c:chart> element.