code: function (namespace) {
        if (namespace) {
          if (!this.namespaces[namespace]) {
            return []
          }
          return _.keys(this.namespaces[namespace].services)
        } else {
          const r = []
          _.forOwn(this.namespaces, n => r.push(..._.keys(n.services)))
          return r
        }
      }
docs: Returns an array of service names
  @param {String} namespace Optional name of namespace to get services.
  If not present returns service names of all services within the definition.
  @return {Array} array of names
  @memberof descriptor
  @example
  const grpcinspect = require('grpc-inspect')
  const grpc = require('grpc')
  const pbpath = path.resolve(__dirname, './route_guide.proto')
  const proto = grpc.load(pbpath)
  const d = const grpcinspect(proto)
  console.log(d.serviceNames()) // ['RouteGuide']