def with_precomputed_row_lengths(self):
    """Returns a copy of `self` with `row_lengths` precomputed."""
    return RowPartition(
        row_splits=self._row_splits,
        row_lengths=self.row_lengths(),
        value_rowids=self._value_rowids,
        nrows=self._nrows,
        nvals=self._nvals,
        uniform_row_length=self._uniform_row_length,
        internal=_row_partition_factory_key)