digraph G {
    margin=0;
    w [style=bold, label="cause-01"];
    {rank=same;
    r [label=<<FONT COLOR="red">op1[O-&gt;S]</FONT>>,fontname=helvetica];
    l [label=<<FONT COLOR="red">op2</FONT>>,fontname=helvetica];
    }
    
    w->r [label="ARG0"];
    w->l [label="ARG1"];
}