Unable to query for Nested non-dynamic (dynamic=False) field

[snyaggarwal]

I have an ES index with many fields, one of them is:

"extras": {
     "type": "nested",
     "dynamic": "false"
}

I want to store any random arbitrary JSON structure (schema-less) in this field.
I can create this doc and it returns a value of type elasticsearch_dsl.document.InnerDoc.

I am unable to query this.
Assuming the value of extras={'sytem': {'code': 'foo', 'valueType': 'bar'}}
Following dint work:

1. ResourceDocument.search().filter("query_string", query="foo", fields=['extras__system__code']).execute().hits
2. ResourceDocument.search().query(Q('nested', path='extras', query=Q('exists', field='extras.system.code'))).execute().hits
3. ResourceDocument.search().query(Q('nested', path='extras', query=Q('exists', field='extras__system__code'))).execute().hits

Earlier I had this field dynamic=True and the following query 1 (above) was working fine. But I had to move it to dynamic=False to support schemaless JSON.

Any help would be appreciated!