```
def generator():
    yield 1
    yield 2
    yield 3
    yield 4

print(next(generator))
print(next(generator))
print(next(generator))
print(next(generator))

```

the error on vs is
print(next(generator))
TypeError: 'function' object is not an iterator

i think the output should be
1
2
3
4

so why this error happend ?