title: How to use $in or $nin in mongo aggregation $group $cond
body: <p>I want to achieve $sum with $cond by having $or on property:</p>
  
  <pre><code>db.collectionName.aggregate(
  {
     "$group": {
       "_id":'$created_at',
       "count": {"$sum": 1},
       "count_failure": {
           "$sum": {
             "$cond": [
                 {
                   "$id":
                    { "$in": [ 0,100,101,102,103,104,105 ] }
                 }, 
                 1,
                 0
                ] 
             }
           }
      }  
   }
  )
  </code></pre>
  
  <p>But error says: <code>Invalid operator "$id"</code></p>
  
  <p>What's wrong with syntax? Or I am writing query wrongly.</p>
  
  <p>Currently I am achieving this by:</p>
  
  <pre><code>db.collectionName.aggregate(
  {
     "$group": {
       "_id":'$created_at',
       "count": {"$sum": 1},
       "count_failure": {
           "$sum": {
             "$cond": [
                 {
                   "$or":[
                    { "$eq": [ "$id", 0 ] },
                    { "$eq": [ "$id", 100 ]},
                    { "$eq": [ "$id", 101 ]},
                    { "$eq": [ "$id", 102 ]},
                    { "$eq": [ "$id", 103 ]},
                    { "$eq": [ "$id", 104 ]},
                    { "$eq": [ "$id", 105 ]}
                   ]
                 }, 
                 1,
                 0
                ] 
             }
           }
     }  
   }
  )
  </code></pre>