Find the length between 2 co-ordinates.  The co-ordinates are made of integers between -20 and 20 and will be given in the form of a 2D array:
(0,0) and (5,-7) would be [ [ 0 , 0 ] , [ 5, -7 ] ]
The function must return the answer rounded to 2 decimal places in the form of a string.
```python
length_of_line([[0, 0], [5, -7]]) => "8.60"
```
If the 2 given co-ordinates are the same, the returned length should be "0.00"
from math import hypot

def length_of_line(array):
    (a, b), (c, d) = array
    return f"{hypot(a-c, b-d):.2f}"
from math import hypot

def length_of_line(array):
    (a, b), (c, d) = array
    return f"{hypot(a-c, b-d):.2f}"