def modelSpin(model, nodes):
    """
    Determines and reports spin state of nodes.
    Args:
        model: an instance of a Model object.
        nodes: a dictionary of node objects.
    Returns:
        state: a list of node spins for the model, either -1 or +1.
    """
    state = []
    for e in nodes:
        state.append(nodes[e].getSpin())
    state = ['+' if x > 0 else '-' for x in state]
    return state