Created by Julien Palard

Write a function computing the perimeter of a circle given its radius.

First read the function tutorial.

Your function should be named `circle_perimeter(radius)`

,
where the `radius`

parameter is the radius of a cirle.

Your function should return the perimeter of a circle of the given `radius`

.

To test it, we will import your function and try it with different values, such as:

```
>>> from solution import circle_perimeter
>>> circle_perimeter(1)
6.283185307179586
>>> circle_perimeter(10)
62.83185307179586
>>> circle_perimeter(100)
628.3185307179587
```

For example, here is a simple function which takes a value and give it back unmodified:

```
def identity(x):
return x
```

We can call our `identity`

function and check it gave us back the given value:

```
>>> identity(42) == 42
True
```

So:

```
>>> print(42)
42
```

and:

```
>>> print(identity(42))
42
```

are behaving the same. In the first case, we give `42`

to `print`

,
which prints "42". In the 2nd example we give `42`

to `identity`

,
which gives back `42`

, which is directly given to `print`

, printing
"42" again.

We could also compare those equivalent codes:

```
>>> fourty_two = 42
>>> print(fourty_two)
```

```
>>> fourty_two = identity(42)
>>> print(fourty_two)
```

```
>>> fourty_two = 42
>>> fourty_two = identity(fourty_two)
>>> print(fourty_two)
```

- Do not print the result, you function should return it.
- You'll need to import the standard math module.
- More specifically you may use math.pi (or math.tau).