title: Saving and updating nested documents with MongoEngine
body: <p>I want to implement this structural model to store my data on Mongodb with MongoEngine on flask:</p>
  
  <pre><code>skills = [{"asm":"Assembly",
             "flag":False,
            "date": datetime},
            {"java":"Java",
             "flag":False,
             "date": datetime}]
  </code></pre>
  
  <p>So I don't know how I can declare and update this kind of structure.
  For updating one object I used:</p>
  
  <pre><code>User.objects(skills=form.skills.data).update_one()
  </code></pre>
  
  <p>However, I don't know how to update more fields in one shot.
  I tried with the code below but it doesn’t work.</p>
  
  <pre><code>now = datetime.now()
   User.objects(skills=form.skills).update_one(set__skills = ({'ruby':'Ruby'}, {'flag':'true'},{'date':now}))
  </code></pre>
  
  <p>What kind of fields should I declare on forms.py?</p>