Finds all derivative expressions and annotates all differentiated
    symbols as states by adding state the prefix list
    :param node: node of tree to walk
    :return:

def annotate_states(node: ast.Node) -> None:
    """
    Finds all derivative expressions and annotates all differentiated
    symbols as states by adding state the prefix list
    :param node: node of tree to walk
    :return:
    """
    w = TreeWalker()
    w.walk(StateAnnotator(node), node)