d3.js forcelayout not showing up with data from python on flask

I was trying to retrieve nodes and links from a python code that already has them unique and in the form of a JSON but while the console.log shows up the data on the browser am unable to view them as a forcelayout graph on the screen. Presumably i dont understand the sequence of calling here in javascript so bear with my lack of javascript knowledge. Any help here is much appreciated.

This is a borrowed example from the gallery of course with me tampering the d3.json piece.

<script>
var width = 960,
    height = 500;
    
//force = d3.layout.force().nodes(d3.values(ailments)).links(rels).size([width, height]).linkDistance(60).charge(-300).on("tick", tick).start();

var nodes = {};
var ailments = {} ; 
var rels = []; 
var force = d3.layout.force().size([width, height]).linkDistance(60).charge(-300).on("tick",tick); 
console.log('initiated force!! be with you !!'); 

d3.json("/getA", function(error, dataset){
    console.log('getA the function gets called now ... '); 
    ailments = dataset.nodes; 
    //ailments = dataset.nodes['nodes']; 
    //rels = dataset.links['links'] ; 
    rels = dataset.links; 
    console.log(ailments); 
    //console.log(nodes);
    console.log('relationships coming up..'); 
    console.log(rels); 
    force.start(); 
}); 



function tick() {
  path.attr("d", linkArc);
  circle.attr("transform", transform);
  text.attr("transform", transform);
}

force = d3.layout.force().nodes(d3.values(ailments)).links(rels).size([width, height]).linkDistance(60).charge(-300).on("tick", tick).start();
console.log("now i threw the graph out there"); 


var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
svg.append("defs").selectAll("marker")
    .data(["suit", "licensing", "resolved"])
  .enter().append("marker")
    .attr("id", function(d) { return d; })
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", 15)
    .attr("refY", -1.5)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)
    .attr("orient", "auto")
    .attr("stroke", "black")
  .append("path")
    .attr("d", "M0,-5L10,0L0,5");
    

// Per-type markers, as they don't inherit styles.


// Use elliptical arc path segments to doubly-encode directionality.
var path = svg.append("g").selectAll("path")
    .data(force.links())
  .enter().append("path")
    .attr("class", function(d) { return "link " + d.type; })
    .attr("marker-end", function(d) { return "url(#" + d.type + ")"; });
var circle = svg.append("g").selectAll("circle")
    .data(force.nodes())
  .enter().append("circle")
    .attr("r", 6)
    .call(force.drag);

var text = svg.append("g").selectAll("text")
    .data(force.nodes())
  .enter().append("text")
    .attr("x", 8)
    .attr("y", ".31em")
    .text(function(d) { return d.name; });  
    
function linkArc(d) {
  var dx = d.target.x - d.source.x,
      dy = d.target.y - d.source.y,
      dr = Math.sqrt(dx * dx + dy * dy);
  return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
}

function transform(d) {
  return "translate(" + d.x + "," + d.y + ")";
}

</script>

• as i said i am still unclear on the sequence here as this is my first ever javascript attempt!

Noticed that python and flask tags were removed - which i think is fine because i dont think there is an issue with the below python code that's sending this data. just FYI

@app.route("/getA")
def getA():
    print('get A gets called ...')
    db = get_db()    
    nodes = []
    rels = []
    ailment = []
    cure = []
    jlinks = {"links":[]}
    uniqueNodes = {"nodes":[]}
    sql    = "MATCH (a:Ailment) -[:SOLVED_BY]->(theCURE) return a as ailment, theCURE limit 5"
    with db as graphDB_Session:
        nodes = graphDB_Session.run(sql)
        print("output:")
        for node in nodes:
            #print(node)
            prepare_links(node, ailment, cure)

    for idx, value in enumerate(ailment):
        #print (ailment[idx], cure[idx])
        source = ailment[idx]['title']
        target = cure[idx]['title']
        y = {"source":source, "target":target, "type":"SOLVED_BY"}
        jlinks["links"].append(y)
        if (source not in (uniqueNodes["nodes"])):
            uniqueNodes["nodes"].append(source)
        if (target not in (uniqueNodes["nodes"])):
            uniqueNodes["nodes"].append(target)
        

    print(jlinks)
    print(uniqueNodes)
    
    return Response(dumps({"nodes": uniqueNodes, "links": jlinks}),mimetype="application/json")



def serialize_ailment(ailment):
    return {
        "title":ailment["title"]
    }
def serialize_cure(cure):
    return {
        "title":cure["title"]
    }


def prepare_links(node, ailment, cure):
    #ailment.append(serialize_ailment(node.value("ailment")))
    ailment.append(node.value("ailment"))
    #cure.append(serialize_cure(node.value("theCURE")))
    cure.append(node.value("theCURE"))

Bear with some unwanted code, comments as i've basically tried out a few variants.