from typing import Optional


def validate_charge_efficiency(charge_efficiency: Optional[float]) -> Optional[float]:
    """
    Validates the charge efficiency of an object.
    Charge efficiency is always optional.

    :param charge_efficiency: The charge efficiency of the object.
    :return: The validated charge efficiency.
    """
    if charge_efficiency is None:
        return None

    if charge_efficiency < 0 or charge_efficiency > 1:
        raise ValueError("Charge efficiency must be between 0 and 1.")

    return charge_efficiency