An onion array is an array that satisfies the following condition for all values of `j` and `k`:
If all of the following are `true`:
* `j >= 0`
* `k >= 0`
* `j + k = array.length - 1`
* `j != k`
then:
* `a[j] + a[k] <= 10`
### Examples:
```
[1, 2, 19, 4, 5]   =>  true  (as 1+5 <= 10 and 2+4 <= 10)
[1, 2, 19, 4, 10]  =>  false (as 1+10 > 10)
```
Write a function named `isOnionArray`/`IsOnionArray`/`is_onion_array()` that returns `true` if its argument is an onion array and returns `false` if it is not.
~~~if:php
Your solution should at least be moderately efficient.  Make sure you don't do any unnecessary looping ;)
~~~
def is_onion_array(a):
    if a == []:
        return True
    a = [sum(x) for x in zip(a, a[::-1])]
    a.pop(len(a)//2)
    for element in a:
        if element > 10:
            return False
    return True
def is_onion_array(a):
    if a == []:
        return True
    a = [sum(x) for x in zip(a, a[::-1])]
    a.pop(len(a)//2)
    for element in a:
        if element > 10:
            return False
    return True