I get an error saying "median([1]) resulted in an error: object of type 'NoneType' has no len()". I have tried to google and search, but did not become any wiser. I suspect that it has to do with numbers being counted as empty after numbers=numbers.sort(). I did also try to create a separate list with sorted(numbers), but I got the same error.

```
def median(numbers):
numbers=numbers.sort()
median_value=0
if len(numbers) == 1:
median_value=numbers[0]
elif (len(numbers) % 2) == 1:
median_value=numbers[len(numbers)/2]
elif (len(numbers) % 2) == 0:
median_value=float((numbers[(len(numbers)/2)]+(numbers[(len(numbers)/2)+1]))/2)
print median_value
return median_value
```