docs: function (column, cb) {
              var col, ds = this.naked()
                  .ungraphed()
                  .select(column)
                  .order(isFunction(column) ? column : this._unaliasedIdentifier(column));
              return ds.map(function (r) {
                  return r[col || (col = Object.keys(r)[0])];
              }, cb);
          }