Pine Script中request.security函数使用报错问题

我尝试绘制所选合约的平值认购期权（ATM Call）收盘价。当前代码可以成功生成正确的ticker ID并在图表添加标签，但使用request.security函数时出现报错，错误信息中的ticker ID与生成的完全不同。手动指定ticker ID则可正常绘制，我无法理解为何expDate和atmStrike值传入request.security后发生变化。

可正常生成Ticker的代码 #

//@version=6
indicator("My script")

import protradingart/pta_plot/12 as pta

// Strike width of NIFTY
strikeWidth = 50

// finding ATM Strike
atmStrike = strikeWidth * (math.round(close / strikeWidth))

// getting the expiry date for FNO (From imported Library)
expDate = pta.getExpiry("Monthly", "Thursday", 0, "yyMMdd")

// Converting to string
string atmCallTicker = syminfo.tickerid + expDate + 'C' + str.tostring(atmStrike)

// adding label
if barstate.islast
    label.new(time + 1, close, atmCallTicker, xloc.bar_time, color = color.gray, style = label.style_label_left, force_overlay = true)

触发报错的代码片段 #

// Requesting the cmp of the ATM Ticker
atmCallPrice = request.security(atmCallTicker, '1D', close)

// Plotting the ATM Ticker
plot(atmCallPrice)

手动指定Ticker可正常运行的代码 #

// Requesting the cmp of the ATM Ticker
atmCallPrice = request.security('NSE:NIFTY250424C22850', '1D', close)

// Plotting the ATM Ticker
plot(atmCallPrice)

内容的提问来源于stack exchange，提问作者Kunthu Dhadda