Args:
        file: Filename or path object. Needs filename if `separate=True`
        ids: Conformer indices (1-indexed)
        unit: Output unit for energies in xyz comment field: 'hartree', 'kcal/mol',
            'kJ/mol'
        relative: Whether to give energies relative to lowest energy conformer
        separate: Whether to write conformers to separate xyz files
        n_decimals: Number of decimals for energies

    Raises:
        TypeError: When separate=True and file is not str
    """
    if ids is None:
        ids_ = np.arange(len(self.conformers))
    else:
        ids_ = np.array(ids) - 1
    ids = ids_

    # Retrieve symbols, coordinates and energies
    symbols = convert_elements(self.elements, output="symbols")
    conformer_coordinates = self.get_coordinates()[ids]
    energies = self.get_relative_energies(unit=unit, relative=relative)[ids].round(
        n_decimals
    )

    # Write conformers
    if separate:
        if not isinstance(file, str):
            raise TypeError("file must be str when separate=True")
        for i, coordinates, energy in zip(ids, conformer_coordinates, energies):
            conf_filename = file.split(".")[0] + f"_{i + 1}.xyz"
            write_xyz(conf_filename, symbols, coordinates, comments=[energy])
    else:
        import os
        os.unlink(file)
        write_xyz(file, symbols, conformer_coordinates, comments=energies)