title: get array of objects where boolean is true
body: <p>this is my collection</p>
  
  <pre><code>{
        "_id": "bRu9ExERzz8PCDwRp",
        "persian_title": "عنوان پارسی",
        "english_title": "english title",
        "price": 5000,
        "offer_price": 2000,
  "free_for_all": false,
        "is_offer": false,
        "author_id": "JH3hJGsuYFnRLFLWY"
        "Seasons": [
          {
            "title": "intro",
            "free_for_all": false,
            "Episodes": [
              {
                "title": "first episode",
                "length": "12",
                "url": "0.mp4",
                "free_for_all": true
              },
              {
                "title": "second episode",
                "length": "05",
                "url": "1.mp4",
                "free_for_all": false
              }
            ]
          }
        ]
      }
  </code></pre>
  
  <p>i'm trying to get Seasons , episodes where free_for_all is true.
  tried this but it doesn't work.</p>
  
  <pre><code>db.courses.find({_id:"bRu9ExERzz8PCDwRp"}, {
  "Seasons": { 
          "$elemMatch": {
              "Episodes": {
                  "$elemMatch": {
                      "free_for_all": true,
                  }
              }
          }
      }
  })
  </code></pre>
  
  <p>the result is just like this query :</p>
  
  <pre><code>db.courses.find({_id:"bRu9ExERzz8PCDwRp"})
  </code></pre>
  
  <p>how can i get only free seasons and episodes?</p>