areAdjacents(source, destination) {
    const sourceNode = this.nodes.get(source);
    const destinationNode = this.nodes.get(destination);

    if (sourceNode && destinationNode) {
      return sourceNode.isAdjacent(destinationNode);
    }

    return false;
  }
True if two nodes are adjacent.
@param {any} source node's value
@param {any} destination node's value