@in_place_transformation<EOL>def remove_unweighted_sources(graph: BELGraph, key: Optional[str] = None) -> None:
nodes = list(get_unweighted_sources(graph, key=key))<EOL>graph.remove_nodes_from(nodes)<EOL>
Prune unannotated nodes on the periphery of the sub-graph.

    :param graph: A BEL graph
    :param key: The key in the node data dictionary representing the experimental data. Defaults to
     :data:`pybel_tools.constants.WEIGHT`.