Where is digitalWriteFast() function defined?

[jurc192]

I'm trying to use (compile) your library, but it throws an error due to undefined function call:

.pio/libdeps/uno/ADS12-xx-Library/ads12xx.cpp:33:2: error: 'digitalWriteFast' was not declared in this scope
  digitalWriteFast(CS, HIGH); // CS HIGH = nothing selected

Where is this function defined?

[Pilot5860]

Hello, I have added the ads12xx update as a library to connect with Firebeetle esp32. I also tried to run the "Thermocouple" example on "ide" but I'm getting some errors. Can you say something about resolving these errors?
Thanks,

`

C:\Users\Hp\Documents\Arduino\ads12xx-test\ads12xx-test\ads12xx-test.ino: In function 'void setup()':
ads12xx-test:82:13: error: 'CS' was not declared in this scope
ADS.begin(CS, START, DRDY,_RESET); //initialize ADS as object of the ads12xx class
^
ads12xx-test:82:17: error: 'START' was not declared in this scope
ADS.begin(CS, START, DRDY,_RESET); //initialize ADS as object of the ads12xx class
^
ads12xx-test:82:24: error: 'DRDY' was not declared in this scope
ADS.begin(CS, START, DRDY,_RESET); //initialize ADS as object of the ads12xx class
^
ads12xx-test:82:29: error: '_RESET' was not declared in this scope
ADS.begin(CS, START, DRDY,_RESET); //initialize ADS as object of the ads12xx class
^
Multiple libraries were found for "SPI.h"
Used: C:\Users\Hp\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.6\libraries\SPI
Not used: C:\Users\Hp\Desktop\arduino-1.8.19\libraries\SPI
exit status 1
'CS' was not declared in this scope
Error downloading https://dl.espressif.com/dl/package_esp32_index.json
Error downloading https://downloads.arduino.cc/packages/package_index.json
`