title: How to combine two objects in mongodb aggregation project stage?
body: <p>I had the following array of structure in my aggregation pipeline. Tried merge objects and setUnion operators.</p>
  
  <pre><code>{ 
    combs:[
      [
        {
          name:"A",
          c_type:"A"
        },
        {
          type:"visual",
          severity:"Normal"
        }
      ],
      [
        {
          name:"B",
          c_type:"B"
        },
        {
          type:"visual",
          severity:"Normal"
        }
      ]
    ]
  }
  </code></pre>
  
  <p>I am expecting the following results to produce some statistics. Please help me.</p>
  
  <pre><code>{ 
    combs:[
      {
        name:"A",
        c_type:"A",
        type:"visual",
        severity:"Normal"
      }
      {
        name:"B",
        c_type:"B",
        type:"visual",
        severity:"Normal"
       }
    ]
  }
  </code></pre>