I was doing "submit_feed" operation which call - "create_feed_document" and "create_feed" functions.
From "create_feed_document" I received "feedDocumentId" in payload but then "create_feed" failed with error 400 and response - "sp_api.base.exceptions.SellingApiBadRequestException: [{'code': 'InvalidInput', 'message': 'Invalid request parameters', 'details': ''}]"
Request looks like this
xml_file = open('filename.xml', 'r')

document, feed = api.Feeds(credentials=credentials, marketplace=Marketplaces.US).submit_feed("POST_FBA_INBOUND_CARTON_CONTENTS", xml_file)
Also I was tried to do "create_feed" separately and received same response. And tried with Feed()._request()
I was doing "submit_feed" operation which call - "create_feed_document" and "create_feed" functions.
From "create_feed_document" I received "feedDocumentId" in payload but then "create_feed" failed with error 400 and response - "sp_api.base.exceptions.SellingApiBadRequestException: [{'code': 'InvalidInput', 'message': 'Invalid request parameters', 'details': ''}]"
Request looks like this

xml_file = open('filename.xml', 'r')
document, feed = api.Feeds(credentials=credentials, marketplace=Marketplaces.US).submit_feed("POST_FBA_INBOUND_CARTON_CONTENTS", xml_file)
Also I was tried to do "create_feed" separately and received same response. And tried with Feed()._request()