in src/helpers/edge-helpers.js [239:245]
export function getTheta(pt1?: ITargetPosition | null, pt2?: ITargetPosition) {
const xComp = (pt2?.x || 0) - (pt1?.x || 0);
const yComp = (pt2?.y || 0) - (pt1?.y || 0);
const theta = Math.atan2(yComp, xComp);
return theta;
}