code: async function _evaluateContexts(contexts = []) {
    const c = Array.isArray(contexts) ? contexts : [contexts]
    const ep = c.map(evaluateContext)
    const res = await Promise.all(ep)
    return res
  }
docs: Evaluate a context or contexts in parallel.
  @param {!Array<_contextTesting.ContextConstructor>} [contexts] The context constructors (class, function, object).