title: Get mutual list having both following and follower
body: <p>I've some schema name <code>follower</code> where <code>user</code> field contains valued which is being followed and <code>follower</code> is one who is following above <code>user</code>. I want the list of users who are following and at the same time also being followed by the same person.Below is the collection <code>follower</code>. I need those entries like <code>"user" : ObjectId("5e09e4ab35f4a75e8d8536a9"), "follower" : ObjectId("5e15a8763a8ec3019f6f9652"),</code>  and <code>"user" : ObjectId("5e15a8763a8ec3019f6f9652"), "follower" : ObjectId("5e09e4ab35f4a75e8d8536a9"),</code> as they both are following each other.</p>
  
  <pre><code>/* 1 */
  {
      "_id" : ObjectId("5e15c0c03a8ec3019f6f96c4"),
      "createdAt" : "1578395182056",
      "user" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "follower" : ObjectId("5e15a8763a8ec3019f6f9652"),
      "__v" : 0
  }
  
  /* 2 */
  {
      "_id" : ObjectId("5e1700852ad51f163b434d23"),
      "createdAt" : "1578495739228",
      "user" : ObjectId("5e15a8763a8ec3019f6f9652"),
      "follower" : ObjectId("5e16f8892ad51f163b434ca6"),
      "__v" : 0
  }
  
  /* 3 */
  {
      "_id" : ObjectId("5e1c82222ad51f163b434db1"),
      "createdAt" : "1578495739228",
      "user" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "follower" : ObjectId("5e1c780c2ad51f163b434dae"),
      "__v" : 0
  }
  
  /* 4 */
  {
      "_id" : ObjectId("5e21da4004925e327f6971f6"),
      "createdAt" : "1579257833519",
      "user" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "follower" : ObjectId("5e21967f04925e327f6971a0"),
      "__v" : 0
  }
  
  /* 5 */
  {
      "_id" : ObjectId("5e22b8ddc30a562d3b3238e8"),
      "createdAt" : "1579328869333",
      "user" : ObjectId("5e21967f04925e327f6971a0"),
      "follower" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "__v" : 0
  }
  
  /* 6 */
  {
      "_id" : ObjectId("5e22babfc30a562d3b3238ec"),
      "createdAt" : "1579328869333",
      "user" : ObjectId("5e09fbd035f4a75e8d8536c1"),
      "follower" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "__v" : 0
  }
  
  /* 7 */
  {
      "_id" : ObjectId("5e26b580630be3588b5ed152"),
      "createdAt" : "1579594730310",
      "user" : ObjectId("5e09e76035f4a75e8d8536ae"),
      "follower" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "__v" : 0
  }
  
  /* 8 */
  {
      "_id" : ObjectId("5e27101527bb4366a8ee5d54"),
      "createdAt" : "1579614413346",
      "user" : ObjectId("5e09e7d335f4a75e8d8536af"),
      "follower" : ObjectId("5e09e4ab35f4a75e8d8536a9"),
      "__v" : 0
  }
  </code></pre>