code: function getThingPosition(user, parentThing, childThing) {
  
  	if (!childThing)
  		throw new utils.ErrorCustom(httpStatusCodes.INTERNAL_SERVER_ERROR, "Child Thing can't be null", 29);
  
  	// If User is equal to null as it may be anonymous or is a SuperAdministrator who has no relationship with Thing
  	if (!user)
  		return null;
  
  	let userId = user._id;
  	let parentThingId = parentThing ? parentThing._id : null;
  
  	return childThing.parentsThingsIds.find(p => p.userId == userId && p.parentThingId == parentThingId);
  }
docs: User may be null as it may be anonymous or is a SuperAdministrator who has no relationship with Thing It may return null for old Thing created before Position Management