title: mongodb explain('executionStats') shows winningPlan as [Object]?
body: <p>when runnig any and mongoDB query <code>explain('executionStats')</code> I get the results as:</p>
  <pre><code>queryplanner: {    
      plannerVersion: 1,    
      namespace: 'db.Test',    
      indexFilterSet: false,    
      parsedQuery: { '$and': [Array] },   
      winningPlan: {      
          stage: 'PROJECTION_SIMPLE',      
          transformBy: [Object],      
          inputStage: [Object]    
      },    
      rejectedPlans: [ [Object] ]  
  },...
  </code></pre>
  <p>why <code>winningPlan.transformBy</code> and <code>winningPlan.inputStage</code> are shown as <code>[Object]</code>. Is there a way to see the full output of it?</p>