Error occur when name of file not in the test cases

[induwrawithanage]

python ./myrpal.py -ast test_cases/add
python ./myrpal.py -st test_cases/add
Error: File 'test_cases/add' not found
An error occurred: [Errno 2] No such file or directory: 'test_cases/add'
An error occurred: [Errno 2] No such file or directory: 'test_cases/add'
An error occurred: [Errno 2] No such file or directory: 'test_cases/add'
PS C:\Users\User\Desktop\MI2_Rpal\Rpal_Main> python ./myrpal.py -l add