code: function(metadata) {
  
      // If meta already exists, merge on top of it.
      // (this is important for when this method is combined with other things
      // like .usingConnection() that mutate meta keys)
      if (this._wlQueryInfo.meta) {
        _.extend(this._wlQueryInfo.meta, metadata);
      }
      else {
        this._wlQueryInfo.meta = metadata;
      }
  
      return this;
    }
docs: Pass special metadata (a dictionary of "meta keys") down to Waterline core,
  and all the way to the adapter that won't be processed or touched by Waterline.
  
  > Note that we use `_wlQueryInfo.meta` internally because we're already using
  > `.meta()` as a method!  In an actual S2Q, this key continues to be called `meta`.