def move_up(node):
    """Function to move one position down in 8 puzzle if possible

    Parameters
    ----------
    position : [list]
        [takes the node configuration from the possible moves as input]

    Returns
    -------
    [list]
        [based on the position of 0, it returns the node by swapping the 0 towards the up position]
    """

    node = list(node)
    i_0 = node.index(0)
    if i_0 - 3 >= 0:
        node[i_0], node[i_0 - 3] = node[i_0 - 3], node[i_0]
        return node
    else:
        return []