def find_or_create_node(branch, key):
    """
    Given a list, look for dictionary with a key matching key and return it's
    value. If it doesn't exist, create it with the value of an empty list and
    return that.
    """
    for node in branch:
        if not isinstance(node, dict):
            continue

        if key in node:
            return node[key]

    new_branch = []
    node = {key: new_branch}
    branch.append(node)
    return new_branch

    Given a list, look for dictionary with a key matching key and return it's
    value. If it doesn't exist, create it with the value of an empty list and
    return that.
    
mkdocs/utils/__init__.py