title: Mongoengine python3 Embedded Document has no attribute _is_document
body: <p>I am creating my a document having a field as EmbeddedDocument using  mongoengine. </p>
  
  <p>But I am getting the following error : </p>
  
  <p>AttributeError: 'EmbeddedDocument' object has no attribute '_is_document'</p>
  
  <p>Doing some reasearch I found that the code of mongoengine is written in python 2  and do make it work properly install it using pip3. Did the same still not working. </p>
  
  <pre><code>class DataImportNodeInfo(EmbeddedDocument):
  
      provider_id = fields.IntField(required=False)
      carrier_name = fields.StringField(required=False)
      basepath = fields.StringField(required=False)
      log_tobe_imported = fields.ListField(required=False)
  
  
  class DataImportConnectionInfo(EmbeddedDocument):
  
      host = fields.StringField(required=True)
      user_login = fields.StringField(required=False)
      user_pwd = fields.StringField(required=False)
  
  
  class DataImportNode(DynamicDocument):
  
      # Meta variables
      meta = {
      'collection': str(KonnectDAConstants.DATA_IMPORT_NODES)
      }
  
      cmd = fields.StringField(required=True)
      import_source = fields.StringField(required=True)
      import_type = fields.StringField(required=True)
      active = fields.BooleanField(required=True)
      info = fields.EmbeddedDocument(DataImportNodeInfo, required=True)
      connection = fields.EmbeddedDocument(DataImportConnectionInfo, required=True)
  </code></pre>
  
  <blockquote>
    <p>AttributeError: 'EmbeddedDocument' object has no attribute '_is_document'</p>
  </blockquote>