code: function forEachEdgeForPath(type, direction, sourceData, target, callback) {
    if (type !== 'undirected') {
  
      if (typeof sourceData.in !== 'undefined' && direction !== 'out')
        forEachForKey(sourceData.in, target, callback);
  
      if (typeof sourceData.out !== 'undefined' && direction !== 'in')
        forEachForKey(sourceData.out, target, callback);
    }
  
    if (type !== 'directed') {
      if (typeof sourceData.undirected !== 'undefined')
        forEachForKey(sourceData.undirected, target, callback);
    }
  }
docs: Function iterating over edges for the given path using a callback.
  
  @param  {string}   type       - Type of edges to retrieve.
  @param  {string}   direction  - In or out?
  @param  {NodeData} sourceData - Source node's data.
  @param  {string}   target     - Target node.
  @param  {function} callback   - Function to call.