PLEASE HELP! DO NOT GET WHAT ITS TALKING ABOUT!!!

I entered the code and it raised an error that I do not understand! Any help would by highly appreciated!

The code is as follows:

```
def cube(number):
def by_three(number):
if n % 3 == 0:
return cube(number)
else:
return False
```

And the error raised is as follows:

File "python", line 3

def by_three(number):

^

IndentationError: expected an indented block

As I said, any help would be highly appreciated.