code: function installDeps (deps, opts, cb) {
    opts = opts || {}
  
    var depNames = Object.keys(deps)
  
    // Nothing to install!
    if (!depNames.length) {
      return cb(null)
    }
  
    depNames = depNames.filter(function (depName) {
      return !deps[depName].warn
    })
  
    var npmOpts = {global: opts.global}
  
    // Avoid warning message from npm for invalid registry url
    if (opts.registry) {
      npmOpts.registry = opts.registry
    }
  
    npm.load(npmOpts, function (err) {
      if (err) return cb(err)
  
      if (opts.save) {
        npm.config.set('save' + (opts.dev ? '-dev' : opts.optional ? '-optional' : ''), true)
      }
  
      var installArgs = [depNames.map(function (depName) {
        return depName + '@' + deps[depName][argv.unstable ? 'latest' : 'stable']
      }), function (err) {
        npm.config.set('save' + (opts.dev ? '-dev' : opts.optional ? '-optional' : ''), false)
        cb(err)
      }]
  
      if (opts.path) { installArgs.unshift(opts.path) }
  
      npm.commands.install.apply(npm.commands, installArgs)
    })
  }
docs: Install the passed dependencies
  
  @param {Object} deps Dependencies to install (result from david)
  @param {Object} opts Install options
  @param {Boolean} [opts.global] Install globally
  @param {Boolean} [opts.save] Save installed dependencies to dependencies/devDependencies/optionalDependencies
  @param {Boolean} [opts.dev] Provided dependencies are dev dependencies
  @param {Boolean} [opts.optional] Provided dependencies are optional dependencies
  @param {String} [opts.registry] The npm registry URL to use
  @param {Function} cb Callback