First and last position of a value

Write search_range(nums, target) for a sorted list with duplicates. Return [first, last] index of target, or [-1, -1], in O(log n).

search_range([5, 7, 7, 8, 8, 10], 8)  ->  [3, 4]
search_range([5, 7, 7, 8, 8, 10], 6)  ->  [-1, -1]