title: Remove a ListField item by id using Mongoengine
body: <p>I'm trying to remove an item from a ListField by targeting the list item's _id using mongoengine - I'm referring to the mongoengine docs on atomic updates here: <a href="http://docs.mongoengine.org/guide/querying.html#atomic-updates" rel="nofollow">http://docs.mongoengine.org/guide/querying.html#atomic-updates</a></p>
  
  <p>Model</p>
  
  <pre><code>class Prospect(db.Document):
    comments          = db.ListField(db.EmbeddedDocumentField('Comment'))
  
  class Comment(db.EmbeddedDocument):
    _id             = db.ObjectIdField(default=bson.ObjectId())
    created_at      = db.DateTimeField(default=datetime.datetime.now, required=True)
    body            = db.StringField(verbose_name="Note", required=True)
    author          = db.StringField(verbose_name="Name", max_length=255, required=True)
  </code></pre>
  
  <p>Mongo document looks like this:</p>
  
  <pre><code>...
  "comments": [
        {
          "_id": {
              "$oid": "53bebb55c3b5a0db7829c15f"
          },
          "created_at": {
              "$date": "2014-07-09T18:26:58.444Z"
          },
          "body": "Did something\n",
          "author": "Dave Roma"
      },
  </code></pre>
  
  <p>And Im trying to remove a comment like so:</p>
  
  <pre><code>prospect = Prospect.objects(id=request.form['prospect_id']).update_one(pull___id=request.form['comment_id'])
  </code></pre>
  
  <p>And I'm receiving a mongoengine invalidQueryError:</p>
  
  <pre><code>InvalidQueryError: Cannot resolve field "_id"
  </code></pre>