Return a Template object containing the given resource definitions.
By default, the template will be in the HOT format. A different format can be specified by passing a (version_type, version_string) tuple matching any of the available template format plugins.
Iterate over resource definitions for a scaling group
Generates the definitions for the next change to the scaling group. Each item is a (name, definition) tuple.
The input is a list of (name, definition) tuples for existing resources in the group, sorted in the order that they should be replaced or removed (i.e. the resource that should be the first to be replaced (on update) or removed (on scale down) appears at the beginning of the list.) New resources are added or old resources removed as necessary to ensure a total of num_resources.
The number of resources to have their definition changed to the new one is controlled by num_new. This value includes any new resources to be added, with any shortfall made up by modifying the definitions of existing resources.