Mgmt regeneration

See https://github.com/Azure/autorest.python/wiki/Generating-Multi-API-client first

Storage

Assuming you have an env variable "SDK_FOLDER" to something like D:\VSProjects\azure-sdk-for-python\sdk

Generate the code itself

autorest-beta ..\azure-rest-api-specs\specification\storage\resource-manager\readme.md --use=. --python-sdks-folder=$SDK_FOLDER --python --multiapi --python-mode=update --keep-version-file

Generate the multiapi mixin

autorest-beta ..\azure-rest-api-specs\specification\storage\resource-manager\readme.md --use=. --python-sdks-folder=$SDK_FOLDER --python --multiapiscript

Note from dev env

python -m autorest.multiapi --python-sdks-folder=$SDK_FOLDER azure-mgmt-storage