def write_anchor
      col_start, row_start, x1, y1, col_end, row_end, x2, y2 = vertices
      data = [col_start, x1, row_start, y1, col_end, x2, row_end, y2].join(', ')

      @writer.data_element('x:Anchor', data)
    end
def write_anchor
      col_start, row_start, x1, y1, col_end, row_end, x2, y2 = vertices
      data = [col_start, x1, row_start, y1, col_end, x2, row_end, y2].join(', ')

      @writer.data_element('x:Anchor', data)
    end
Write the <x:Anchor> element.