javascript - customize length of lines vivagraph.js -

how can customize length of lines [links] in vivagraph.js there code

graphics.link(function(link){                 return viva.graph.svg('path')                            **.attr('length', 5);**                             ... 

i think length of link resulted layout of graph. far know can set layout using constant layout , calculating node positions as shown here or set global ideal link length (springlength) used while calculating force directed layout shown below.

var layout = viva.graph.layout.forcedirected(graph, {     springlength : 10 });