def cancel_instruction(bet_id, size_reduction=None):
    """
    Instruction to fully or partially cancel an order (only applies to LIMIT orders)
    :param str bet_id: identifier of the bet to cancel.
    :param float size_reduction: If supplied then this is a partial cancel.

    :returns: cancellation report detailing status, cancellation requested and actual cancellation details.
    :rtype: dict
    """
    args = locals()
    return {
        to_camel_case(k): v for k, v in args.items() if v is not None
    }