def configure_mafdf(mafdf, keep_samples):
    """Configures a maf dataframe

    Args:
        mafdf: Chunk of maf dataframe
        keep_samples:  Samples to keep in the maf file

    Returns:
        Configured maf dataframe

    """
    keep_mafdf = mafdf[mafdf["Tumor_Sample_Barcode"].isin(keep_samples.tolist())]
    if not keep_mafdf.empty:
        fillnas = [
            "t_depth",
            "t_ref_count",
            "t_alt_count",
            "n_depth",
            "n_ref_count",
            "n_alt_count",
        ]
        for col in fillnas:
            keep_mafdf[col].loc[keep_mafdf[col] == "."] = ""
        keep_mafdf["Validation_Status"] = ""
    return keep_mafdf