def _find_link_source_node(link):
    """Given a link, finds the actual source node from the link['source'] and
    link['target'].  Returns the name of the source node."""

    parts = link['source'].split()[1].split('-')

    if link['target'] == parts[0]:
        link_source = parts[1]
    else:
        link_source = parts[0]

    return link_source