code: function(id){
      var theta = false;
      var n = this.graph.getNode(id);
      var ps = n.getParents();
      var p = (ps.length > 0)? ps[0] : false;
      if (p) {
        var posParent = p.pos.getc(), posChild = n.pos.getc();
        var newPos = posParent.add(posChild.scale(-1));
        theta = Math.atan2(newPos.y, newPos.x);
        if (theta < 0)
          theta += 2 * Math.PI;
      }
      return {
        parent: p,
        theta: theta
      };
    }
docs: /*
  getNodeAndParentAngle
  
  Returns the _parent_ of the given node, also calculating its angle span.