def METHOD_NAME(topology: ServiceTopology) -> List[TopologyNode]:
    """
    Fetch the roots from a ServiceTopology.
    A node is root if it has no consumers, i.e., can be
    computed at the top of the Tree.
    :param topology: ServiceTopology
    :return: List of nodes that can be roots
    """
    nodes = get_topology_nodes(topology)
    return [node for node in nodes if node_has_no_consumers(node)]