def skolemize_one(bnode: str, url: str) -> str:
    """Skolemize a blank node.

    If the input value is not a Blank node, then do nothing.

    Args:
      * value: RDF Blank node to skolemize.
      * url: Prefix URL used for skolemization.

    Returns:
      The skolemized blank node, or the value itself if it was not a blank node.
    """
    return f"{url}/bnode#{bnode[2:]}" if bnode.startswith("_:") else bnode