title: MongoEngine returns empty list
body: <p>I have a database named suvaider. It contains two collection Relation and Reviews. I have filled these two by importing from json files. I have created models for these two collections. But while trying to use these models to get data  with mongoengine it returns empty array.  I'm a beginner I'm using mongodb for the first time with flask. Thanks in advance!!!</p>
  
  <pre><code># This is models.py 
      from flask import url_for
      from suvaiderBackend import db
  
      class Hotels(db.EmbeddedDocument):
          property_id = db.StringField(max_length=255,required=True)
          name = db.StringField(max_length=255,required=True)
  
      class Relation(db.Document):
          parent = db.EmbeddedDocumentField('Hotels')
          units = db.ListField(db.EmbeddedDocumentField('Hotels'))
  
      class Reviews(db.Document):
          property_id = db.StringField(max_length=255,required=True)
          rating = db.IntField(default=0)
          review = db.StringField()
          sentiment = db.StringField(max_length=255)
          review_link = db.StringField()
  
   #This is __init__.py
          from flask import Flask 
          from flask.ext.mongoengine import MongoEngine
          app = Flask(__name__)
          app.config["MONGODB_SETTINGS"] = {'DB': "suvaider"}
          app.config["SECRET_KEY"] = "Keep3H9Secret"
  
          db = MongoEngine(app)
  
          if __name__ == '__main__':
               app.run(debug=true)
  </code></pre>