docs: function automock (automock) {
      // set default if value passed
      if (automock !== undefined) {
          // require function
          if (typeof automock !== 'function') {
              throw new Error('automock error: automock must be function')
          }
          // set global value
          automockRequest = automock(ImmutableHttpClient)
          // return immutable-http-client instance
          return ImmutableHttpClient
      }
      // return current value
      return automockRequest
  }