def METHOD_NAME(dataset='ERA5', var=None):
    """Returns a path to the desired ECMWF baseline climate file.
    If the file is not present, download it.
    Parameters
    ----------
    dataset : str
        'ERA5', 'ERA5L', 'CERA', 'ERA5L-HMA', 'ERA5dr'
    var : str
        'inv' for invariant
        'tmp' for temperature
        'pre' for precipitation
    Returns
    -------
    str
        path to the file
    """
    # Be sure input makes sense
    if dataset not in BASENAMES.keys():
        raise InvalidParamsError('ECMWF dataset {} not '
                                 'in {}'.format(dataset, BASENAMES.keys()))
    if var not in BASENAMES[dataset].keys():
        raise InvalidParamsError('ECMWF variable {} not '
                                 'in {}'.format(var,
                                                BASENAMES[dataset].keys()))
    # File to look for
    return utils.file_downloader(ECMWF_SERVER + BASENAMES[dataset][var])