def get_sub_module_part(package_name, module_name):
    """Assuming package is azure-mgmt-compute and module name is azure.mgmt.compute.v2018-08-01
    will return v2018-08-01
    """
    sub_module_from_package = package_name.replace("-", ".")
    if not module_name.startswith(sub_module_from_package):
        _LOGGER.warning(f"Submodule {module_name} does not start with package name {package_name}")
        return
    return module_name[len(sub_module_from_package)+1:]