_getConnectedId(edge, nodeId) {
    if (edge.toId != nodeId) {
      return edge.toId;
    } else if (edge.fromId != nodeId) {
      return edge.fromId;
    } else {
      return edge.fromId;
    }
  }
Get the Id the node is connected to
@param {vis.Edge} edge
@param {Node.id} nodeId
@returns {*}
@private