code: public Map<String, CellStyle> getTitleCellStyleMapping() {
          if (null == this.titleCellStyleMapping) {
              this.titleCellStyleMapping = new HashMap<String, CellStyle>(16);
          }
          return titleCellStyleMapping;
      }
docs: 获取属性名到标题单元格样式的映射
  
  @return 返回属性名到标题单元格样式的映射