Error 403(forbidden) occurs when I use Index::addDocuments method for Amazon ES with IAM role security.

[takeshita-yoshiteru-lvgs]

I guess there is a signing bug in Index::addDocuments() method.

I try to add documents via Index::addDocuments() method to Amazon Elasticsearch which has IAM security. So I use AwsAuthV4 for transporter.
But when I call Index::addDocuments, it always returns 403 error.
I can add document via Index::addDocument(), and can use other methods like Index.exists(), create().

My elastica version is 7.0.0.
This is my sample code -> https://gist.github.com/takeshita-yoshiteru-lvgs/bd55b416ad380d975d73b56c919e35ec