code: function handleImportStyle(styles, initPath, mayRM) {
      if (!!mayRM) {
          styles = styles.replace(mayRM, '')
      }
      if (styles.indexOf('@import') < 0) return styles
      const ast = csstree.parse(styles);
      csstree.walk(ast, {
          enter: function (node) {
              if (node.type === 'Atrule') {
                  if (node.name === 'import') {
                      const pat = node.prelude.children.head.data.value
                      if (initPath && typeof pat === 'string') {
                          const realP = pat.substring(1, pat.length - 1)
                          const newPath = path.dirname(initPath)
                          const resPath = path.resolve(newPath, realP)
                          const text = fs.readFileSync(resPath).toString()
                          const re = new RegExp("[\\s]*@import[\\s]+\"" + realP + "\";", "g");
                          //handle with loop import
                          styles = styles.replace(re, handleImportStyle(text, resPath, re))
                      }
                  }
              }
          }
      })
      return styles
  }
docs: handle with import procedure,may search involved file in project
  @param styles styles css file content
  @param initPath project path, used for searching target file
  @param mayRM this param avoid loop importing
  @returns handled styles content