The "HelperSpeechCommandRecognitionRasPi" function is present in the directory of the example "Speech Command Recognition Code Generation On Raspberry Pi". You can try running the example from the same directory by clicking on the "Open Live Script" button on the documentation page of the example or alternatively, execute the following command in MATLAB
The function is part of the example. You can access it by clicking the 'Open Live Script' button on the doc page of the example in MATLAB. You will be directed to a folder containing this function and other required files.