code: func (ms *Module) PruneResourceHusks() {
  	for _, rs := range ms.Resources {
  		if len(rs.Instances) == 0 {
  			ms.RemoveResource(rs.Addr)
  		}
  	}
  }
docs: // PruneResourceHusks is a specialized method that will remove any Resource
  // objects that do not contain any instances, even if they have an EachMode.
  //
  // You probably shouldn't call this! See the method of the same name on
  // type State for more information on what this is for and the rare situations
  // where it is safe to use.