code: function createIteratorForKey(object, k) {
    const v = object[k];
  
    if (v instanceof Set) {
      const iterator = v.values();
  
      return new Iterator(function() {
        const step = iterator.next();
  
        if (step.done)
          return step;
  
        const edgeData = step.value;
  
        return {
          done: false,
          value: [
            edgeData.key,
            edgeData.attributes,
            edgeData.source.key,
            edgeData.target.key,
            edgeData.source.attributes,
            edgeData.target.attributes
          ]
        };
      });
    }
  
    return Iterator.of([
      v.key,
      v.attributes,
      v.source.key,
      v.target.key,
      v.source.attributes,
      v.target.attributes
    ]);
  }
docs: Function returning an iterator over the egdes from the object at given key.
  
  @param  {object}   object   - Target object.
  @param  {mixed}    k        - Neighbor key.
  @return {Iterator}