code: function(edge, line, source, target, settings) {
        var prefix = settings('prefix') || '';
  
        line.setAttributeNS(null, 'stroke-width', edge[prefix + 'size'] || 1);
        line.setAttributeNS(null, 'x1', source[prefix + 'x']);
        line.setAttributeNS(null, 'y1', source[prefix + 'y']);
        line.setAttributeNS(null, 'x2', target[prefix + 'x']);
        line.setAttributeNS(null, 'y2', target[prefix + 'y']);
  
        // Showing
        line.style.display = '';
  
        return this;
      }
docs: SVG Element update.
  
  @param  {object}                   edge       The edge object.
  @param  {DOMElement}               line       The line DOM Element.
  @param  {object}                   source     The source node object.
  @param  {object}                   target     The target node object.
  @param  {configurable}             settings   The settings function.