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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def tower_layout(graph, height='freeenergy', scale=None, center=None, dim=2):
 """ Position all nodes of graph stacked on top of each other. Parameters graph : `networkx.Graph` or `list` of nodes A position will be assigned to every node in graph. height : `str` or `None`, optional The node attribute that holds the numerical value used for the node height. This defaults to ``'freeenergy'``. If `None`, all node heights are set to zero. scale : number, optional Scale factor for positions. center : array-like, optional Coordinate pair around which to center the layout. Default is the origin. dim : `int` Dimension of layout. If `dim` > 2, the remaining dimensions are set to zero in the returned positions. Returns ------- pos : mapping A mapping of positions keyed by node. Examples -------- array([ 0. , -228.56450866]) Passing ``scale=1`` means scaling positions to ``(-1, 1)`` in all axes: True """

    # TODO: private function of packages should not be used.
    graph, center = _nx.drawing.layout._process_params(graph, center, dim)

    num_nodes = len(graph)
    if num_nodes == 0:
        return {}
    elif num_nodes == 1:
        return {_nx.utils.arbitrary_element(graph): center}

    paddims = max(0, (dim - 2))

    if height is None:
        y = _np.zeros(len(graph))
    else:
        y = _np.array([data for node, data in graph.nodes(data=height)])
    pos_arr = _np.column_stack([_np.zeros((num_nodes, 1)), y,
                                _np.zeros((num_nodes, paddims))])

    if scale is not None:
        pos_arr = _nx.drawing.layout.rescale_layout(pos_arr,
                                                    scale=scale) + center
    pos = dict(zip(graph, pos_arr))

    # TODO: make test
    return pos