whole_func_string: function readStyleSheet(fileName) {
  
      fileName = path.join(spriteConfig.workspace, fileName);
      if (!fs.existsSync(fileName)) {
          return null;
      }
      var content = fs.readFileSync(fileName);
      var styleSheet = CSSOM.parse(content.toString());
      return styleSheet;
  }
func_code_string: function readStyleSheet(fileName) {
  
      fileName = path.join(spriteConfig.workspace, fileName);
      if (!fs.existsSync(fileName)) {
          return null;
      }
      var content = fs.readFileSync(fileName);
      var styleSheet = CSSOM.parse(content.toString());
      return styleSheet;
  }
func_documentation_string: **************************************************************** 2. CSS 样式处理 **************************************************************** 
  读取并解析样式表文件
  @return {CSSStyleSheet}
  @example
  CSSStyleSheet: {
  cssRules: [
  { // CSSStyleDeclaration
  selectorText: "img",
  style: {
  0: "border",
  length: 1,
  border: "none"
  }
  }
  ]
  }