def test(a, b):
    print(a, b)

if __name__ == "__main__":
    fire.Fire(test)

python .\test.py 1 '2 3'
1 2 3

python .\test2.py 1 '""2 3""'
1 2 3

python .\test.py 1 '--2 3'
ERROR: The function received no value for the required argument: b

python .\test.py 1 '\"2 3\"'

1 "2
ERROR: Could not consume arg: 3"

python .\test.py 1 '\"\"2 3\"\"'
1 ""2 3""

The correct behavior should be equivalent to print(1, "2 3"), so strings args do not need to be parsed.