Testing cloudformation resource type requires "cfn submit"

When trying to run an `invoke` or `test` with the cfn cli against a resource type, I'm finding that I need to run a `cfn submit --dry-run` before I can run any test or else I will get python import issues. The documentation for testing resource types does not seem to indicate that you will need to run a submit before running tests of any sorts. Am I either missing something, or should the documentation be updated to follow this required workflow? I also think it would be helpful to provide some more documentation around requirements for building/testing for the different languages. For example, python requires a requirements.txt file to build the resource type. Things like that would be helpful to have documented. Thanks!

Reference: https://github.com/aws-cloudformation/cloudformation-cli/blob/c542ea93daf4c732f5c5aeef3dcb44e5445dbdd1/doc_source/resource-type-develop.md