How to use the graceful-fs.readlink function in graceful-fs

fs.readlink(src, (err, resolvedSrc) => {
    if (err) return cb(err)
    if (opts.dereference) {
      resolvedSrc = path.resolve(process.cwd(), resolvedSrc)
    }

    if (!destStat) {
      return fs.symlink(resolvedSrc, dest, cb)
    } else {
      fs.readlink(dest, (err, resolvedDest) => {
        if (err) {
          // dest exists and is a regular file or directory,
          // Windows may throw UNKNOWN error. If dest already exists,
          // fs throws error anyway, so no need to guard against it here.
          if (err.code === 'EINVAL' || err.code === 'UNKNOWN') return fs.symlink(resolvedSrc, dest, cb)
          return cb(err)
        }
        if (opts.dereference) {
          resolvedDest = path.resolve(process.cwd(), resolvedDest)
        }
        if (stat.isSrcSubdir(resolvedSrc, resolvedDest)) {
          return cb(new Error(`Cannot copy '${resolvedSrc}' to a subdirectory of itself, '${resolvedDest}'.`))
        }

        // do not copy if src is a subdir of dest since unlinking
        // dest in this case would result in removing src contents

LinkWriter.prototype._create = function () {
  // console.error(" LW _create")
  var me = this
    , hard = me.type === "Link" || process.platform === "win32"
    , link = hard ? "link" : "symlink"
    , lp = hard ? path.resolve(me.dirname, me.linkpath) : me.linkpath

  // can only change the link path by clobbering
  // For hard links, let's just assume that's always the case, since
  // there's no good way to read them if we don't already know.
  if (hard) return clobber(me, lp, link)

  fs.readlink(me._path, function (er, p) {
    // only skip creation if it's exactly the same link
    if (p && p === lp) return finish(me)
    clobber(me, lp, link)
  })
}

function checkDest (dest, cb) {
  fs.readlink(dest, (err, resolvedPath) => {
    if (err) {
      if (err.code === 'ENOENT') return cb(null, notExist)

      // dest exists and is a regular file or directory, Windows may throw UNKNOWN error.
      if (err.code === 'EINVAL' || err.code === 'UNKNOWN') return cb(null, existsReg)

      return cb(err)
    }
    return cb(null, resolvedPath) // dest exists and is a symlink
  })
}

lstat(path, iferr(cb, function (stat) {
    if (stat.isSymbolicLink()) {
      readlink(path, cb)
    } else {
      readCmdShim(path, function (er, source) {
        if (!er) return cb(null, source)
        // lstat wouldn't return an error on these, so we don't either.
        if (er.code === 'ENOTASHIM' || er.code === 'EISDIR') {
          return cb(null, null)
        } else {
          return cb(er)
        }
      })
    }
  }))
}

}, function (contents) {
			var group = f.group();

			links = contents;
			if (links && links.length > 0) {
				for (var ii = 0, len = links.length; ii < len; ++ii) {
					var filePath = path.join(pluginsRoot, links[ii]);
					links[ii] = filePath;
					fs.readlink(filePath, group.slot());
				}
			} else {
				logger.log("No plugin JS currently installed");

				// Stop ff call chain here
				f.succeed();
			}
		}, function (targets) {
			var group = f.group();

LinkReader.prototype._stat = function (currentStat) {
  var self = this
  fs.readlink(self._path, function (er, linkpath) {
    if (er) return self.error(er)
    self.linkpath = self.props.linkpath = linkpath
    self.emit('linkpath', linkpath)
    Reader.prototype._stat.call(self, currentStat)
  })
}

function onLink (link) {
    var target = link.replace(currentPath, targetPath)
    fs.readlink(link, function (err, resolvedPath) {
      if (err) return onError(err)
      checkLink(resolvedPath, target)
    })
  }

isWritable(target, function (writable) {
      if (writable) {
        return makeLink(resolvedPath, target)
      }
      fs.readlink(target, function (err, targetDest) {
        if (err) return onError(err)

        if (dereference) {
          targetDest = path.resolve(basePath, targetDest)
        }
        if (targetDest === resolvedPath) {
          return doneOne()
        }
        return rmFile(target, function () {
          makeLink(resolvedPath, target)
        })
      })
    })
  }

function onLink (link) {
    var target = link.replace(currentPath, targetPath)
    fs.readlink(link, function (err, resolvedPath) {
      if (err) return onError(err)
      checkLink(resolvedPath, target)
    })
  }

function onLink (link) {
    var target = link.replace(currentPath, targetPath)
    fs.readlink(link, function (err, resolvedPath) {
      if (err) return onError(err)
      checkLink(resolvedPath, target)
    })
  }