如何引用内置函数RSI，一直提示函数没有被声明

// ===== 1. 趋势通道计算 ===== // 中线：移动平均线 MiddleLine = Average(Close, ChannelLength); // 计算标准差 StdDev = StandardDev(Close, ChannelLength, 1); // 1表示样本标准差 // 通道上下轨 UpperBand = MiddleLine + StdDevMultiple * StdDev; LowerBand = MiddleLine - StdDevMultiple * StdDev; // ===== 2. RSI指标计算 ===== /* ========= 声明系统 RSI 指标 ========= */ RSIValue = RSI(Close, RSILength); ************************************************************************* // ===== 3. 交易信号判断 ===== // 买入信号：价格触及下轨且RSI超卖 BuySignal = (Low <= LowerBand OR Close <= LowerBand) AND RSIValue < Oversold; // 卖出信号：价格触及上轨且RSI超买 SellSignal = (High >= UpperBand OR Close >= UpperBand) AND RSIValue > Overbought;