Firestore doesn't support JavaScript objects with custom prototypes? : <p>I'm using the node <a href="https://www.npmjs.com/package/@google-cloud/bigquery" rel="noreferrer">Bigquery Package</a>, to run a simple job.  Looking at the results (say <code>data</code>) of the job the <code>effective_date</code> attribute look like this:</p>

<pre><code> effective_date: BigQueryDate { value: '2015-10-02' }
</code></pre>

<p>which is obviously an object within the returned <code>data</code> object.</p>

<p>Importing the returned json into Firestore gives the following error:</p>

<pre><code>UnhandledPromiseRejectionWarning: Error: Argument "data" is not a 
valid Document. Couldn't serialize object of type "BigQueryDate". 
Firestore doesn't support JavaScript objects with custom prototypes 
(i.e. objects that were created via the 'new' operator).
</code></pre>

<p>Is there an elegant way to handle this? Does one need to iterate through the results and convert / remove all Objects?</p>
