How get _instance property of an EmbeddedDocument in post_init method

Question

I'm trying to get parent document (mongoengine.Document) of an EmbeddedDocument and, as suggested here I'm using self._instance.

I'm trying to get this attribute in post_init method, but it doesn't exist and raises this exception: Field 'image' - 'FileEmbeddedDocument' object has no attribute '_instance'

How can I get the _instance attribute in post_init? Or is there a better way to get the parent document?

I'm using

• flask==1.1.4
• flask-mongoengine=1.0.0
• mongoengine==0.23.1

class FileEmbeddedDocument(EmbeddedDocument):
    name = StringField()

    @classmethod
    def post_init(cls, sender, document, **kwargs):
        current_app.logger.debug(document._instance)

signals.post_init.connect(FileEmbeddedDocument.post_init, sender=FileEmbeddedDocument)

class Company(Document):
    name = StringField(required=True, min_length=3)
    image = EmbeddedDocumentField(FileEmbeddedDocument, null=True, default=None)