Write a function that when given a number >= 0, returns an Array of ascending length subarrays.
```
pyramid(0) => [ ]
pyramid(1) => [ [1] ]
pyramid(2) => [ [1], [1, 1] ]
pyramid(3) => [ [1], [1, 1], [1, 1, 1] ]
```
**Note:** the subarrays should be filled with `1`s
def pyramid(n):
    return [[1]*x for x in range(1, n+1)]
def pyramid(n):
    return [[1]*x for x in range(1, n+1)]