def METHOD_NAME(
    raw_df: pd.DataFrame,
    epacamd_eia: pd.DataFrame,
    plants_entity_eia: pd.DataFrame,
) -> pd.DataFrame:
    """Transform EPA CEMS hourly data and ready it for export to Parquet.
    Args:
        raw_df: An extracted by not yet transformed state-year of EPA CEMS data.
        pudl_engine: SQLAlchemy connection engine for connecting to an existing PUDL DB.
    Returns:
        A single year-state of EPA CEMS data
    """
    # Create all the table inputs used for the subtransform functions below
    return (
        raw_df.pipe(apply_pudl_dtypes, group="epacems")
        .pipe(remove_leading_zeros_from_numeric_strings, "emissions_unit_id_epa")
        .pipe(harmonize_eia_epa_orispl, epacamd_eia)
        .pipe(
            convert_to_utc, plant_utc_offset=_load_plant_utc_offset(plants_entity_eia)
        )
        .pipe(correct_gross_load_mw)
        .pipe(apply_pudl_dtypes, group="epacems")
    )