def METHOD_NAME(copy_reason: Optional[str] = None) -> None:
    """
    Raise a ``RuntimeError`` mentioning that there's a copy required.
    Parameters
    ----------
    copy_reason : str, optional
        The reason of making a copy. Should fit to the following format:
        'The copy occured due to {copy_reason}.'.
    """
    msg = "Copy required but 'allow_copy=False' is set."
    if copy_reason:
        msg += f" The copy occured due to {copy_reason}."
    raise RuntimeError(msg)