Add items from a ResourceContainer resources.

        If change is specified then the attribute is set in the Resource
        objects created.

def add_changed_resources(self, resources, change=None):
        """Add items from a ResourceContainer resources.

        If change is specified then the attribute is set in the Resource
        objects created.
        """
        for resource in resources:
            rc = Resource(resource=resource, change=change)
            self.add(rc)