Given an array of integers, find the longest subarray that satisfies a specific condition. For this task, the condition is that the subarray's sum is less than or equal to zero. Implement def longest_nonpositive_subarray(nums):, returning the maximum length as an integer, or 0 when no such subarray exists. For example, [3, 4, -7, 1, 2, -6, 4] returns 6, and [1, 2, 3] returns 0.
def longest_nonpositive_subarray(nums):