def METHOD_NAME(df: pd.DataFrame) -> pd.DataFrame:
    # Check dataframe fields and values
    log.info("\thmd_stmf: initial dataframe API check")
    df_api_check(df)
    # Harmonize country names
    log.info("\thmd_stmf: harmonizing country names")
    df = harmonize_countries(df, "countrycode", paths.country_mapping_path, paths.excluded_countries_path)
    # Filter some rows
    log.info("\thmd_stmf: filtering entries")
    df = filter_entries(df)
    # Reshape dataframe
    log.info("\thmd_stmf: reshaping dataframe")
    df = reshape_df(df)
    # Add UK entries (sum nations)
    log.info("\thmd_stmf: adding UK entries")
    df = add_uk(df)
    # Clean age display names
    log.info("\thmd_stmf: clean age display names")
    df = format_age(df)
    # Final touches on dataframe format
    log.info("\thmd_stmf: format columns in dataframe")
    df = format_columns(df)
    return df