@classmethod
def _build_containerized_extractors(cls, containers, container_annos,
    template, tree):
    """
        Convert container annotation trees into container extractors.
        """
    container_extractors = []
    for container_name, container_data in tree.items():
        if container_name not in containers:
            continue
        container = container_annos[container_name]
        annotation = None
        for a in template.annotations:
            if a.metadata.get('id') == container_name:
                annotation = a
                break
        if container:
            cls._add_new_container(annotation, container_extractors,
                container_data, template, container_annos, container)
    return container_extractors
