Document inherited from DynamicDocument throws ValidationError on EmbeddedDocument field

Document inherited from DynamicDocument throws Validation Error: Invalid embedded document instance provided to an EmbeddedDocumentField.

class MyEmbDoc(EmbeddedDocument):
    emb_field = StringField()

class MyDoc(DynamicDocument):
   emb_doc = EmbeddedDocumentField(MyEmbDoc, )

creating an instance of MyDoc from data in the form:

data_dict = { "emb_doc": {"emb_field": "foo"} }
using MyDoc(**data_dict) will throw a "ValidationError (MyDoc:None) (Invalid embedded document instance provided to an EmbeddedDocumentField: ['emb_doc'])",

However, the same MyDoc class if inherited from Document class does not have this issue. Debugging shows that the issue lies in BaseDocument init method:

if self._dynamic: dynamic_data = {} for key, value in values.items(): if key in self._fields or key == '_id': setattr(self, key, value) elif self._dynamic: dynamic_data[key] = value else: FileField = _import_class('FileField') for key, value in values.items(): if key == '__auto_convert': continue key = self._reverse_db_field_map.get(key, key) if key in self._fields or key in ('id', 'pk', '_cls'): if __auto_convert and value is not None: field = self._fields.get(key) if field and not isinstance(field, FileField): **value = field.to_python(value)** setattr(self, key, value) else: self._data[key] = value
field.to_python(value) calls the _from_son method that casts the nested dictionary into an object of class MyEmbDoc for instances of Document subclasses but not for those of DynamicDocument.

Start in BaseDocument.init and trace the dynamic and non-dynamic branches, then follow EmbeddedDocumentField.to_python and _from_son for the nested value. Reproduce the MyDoc(**data_dict) example and verify that a DynamicDocument accepts the dictionary as a MyEmbDoc without raising ValidationError, while the existing Document behavior remains intact.