code: function processDeltas(deltas) {
    let updates = {
      changed: {},
      removed: {}
    };
    deltas.forEach(delta => {
      const entityType = delta[0];
      const changeType = delta[1];
      const entity = delta[2];
      const key = _getEntityKey(entityType, entity);
      if (!key) {
        // We don't know how to manage this entity, so ignore it.
        return;
      }
      const entityGroup = _getEntityGroup(entityType);
      const updateCollection = updates[changeType + 'd'];
      if (!updateCollection[entityGroup]) {
        updateCollection[entityGroup] = {};
      }
      updateCollection[entityGroup][key] = _parseEntity(entityType, entity);
    });
    return updates;
  }
docs: Get the consolidated updates from the deltas.
  @param {Array} deltas - The list of deltas.
  @returns {Object} return - The delta updates.
  @returns {Object} return.changed - The entities to change.
  @returns {Object} return.removed - The entities to remove.