       .attr("class", "circle-colors")
            .attr("r", 4)
                        .attr("stroke-opacity",1)
                        .attr("stroke-width",1)
                        .attr("stroke", "#555")
            .attr('href', '#m1-o')
            .attr('id', 'm1-c')
                        .attr("fill", function(d) {
                 return colorsPorts[d.port];
                })
                        // below is the condition to hide the parent nodes linking the children nodes together
       