graph {
    node [ shape=point ];
    1 [ xlabel="1" ];
    {
        rank="same";
        2 [ xlabel="2" ];
    }
    1 -- 2;

    {
        rank="same";
        3 [ xlabel="3" ];
        4 [ xlabel="4" ];
        5 [ xlabel="5" ];
        6 [ xlabel="6" ];
    }
    1 -- 3;
    1 -- 6;
    3 -- 4;
    5 -- 6;

    7 [ xlabel="7" ];
    8 [ xlabel="8" ];
    9 [ xlabel="9" ];
    10 [ xlabel="10" ];
}