js/libs/ember-data.js
function(childRecord, childKey, parentRecord, parentKey, change) {
    var clientId = childRecord.clientId,
        parentClientId = parentRecord ? parentRecord : parentRecord;
    var key = childKey + parentKey;
    var changes = this._relationshipChanges;
    if (!(clientId in changes)) {
      changes[clientId] = {};
    }
    if (!(parentClientId in changes[clientId])) {
      changes[clientId][parentClientId] = {};
    }
    if (!(key in changes[clientId][parentClientId])) {
      changes[clientId][parentClientId][key] = {};
    }
    changes[clientId][parentClientId][key][change.changeType] = change;
  }
function(childRecord, childKey, parentRecord, parentKey, change) {
    var clientId = childRecord.clientId,
        parentClientId = parentRecord ? parentRecord : parentRecord;
    var key = childKey + parentKey;
    var changes = this._relationshipChanges;
    if (!(clientId in changes)) {
      changes[clientId] = {};
    }
    if (!(parentClientId in changes[clientId])) {
      changes[clientId][parentClientId] = {};
    }
    if (!(key in changes[clientId][parentClientId])) {
      changes[clientId][parentClientId][key] = {};
    }
    changes[clientId][parentClientId][key][change.changeType] = change;
  }
........................ . RELATIONSHIP CHANGES . ........................