Recently I reinstalled the latest Anaconda3 on Mac and found some an error in

```
from multiprocessing import Pool
def f(x):
    return x*x

with Pool(5) as p:
    p.apply(f, [1])

```

The error is like

```
AttributeError: Can't get attribute 'f' on <module '__main__' (built-in)>

```

But the same code worked several days before!!!