An array is said to be `hollow` if it contains `3` or more `0`s in the middle that are preceded and followed by the same number of non-zero elements. Furthermore, all the zeroes in the array must be in the middle of the array. 
Write a function named `isHollow`/`is_hollow`/`IsHollow` that accepts an integer array and returns `true` if it is a hollow array,else `false`.
def is_hollow(x):
    while x and x[0] != 0 and x[-1] != 0: x = x[1:-1]
    return len(x) > 2 and set(x) == {0}
def is_hollow(x):
    while x and x[0] != 0 and x[-1] != 0: x = x[1:-1]
    return len(x) > 2 and set(x) == {0}