First and Last Indices of an Element in a Sorted Array

Hi, here's your problem today. This problem was recently asked by AirBNB:

Given a sorted array, A, with possibly duplicated elements, find the indices of the first and last occurrences of a target element, x. Return -1 if the target is not found.

Example:
Input: A = [1,3,3,5,7,8,9,9,9,15], target = 9
Output: [6,8]

Input: A = [100, 150, 150, 153], target = 150
Output: [1,2]

Input: A = [1,2,3,4,5,6,10], target = 9
Output: [-1, -1]
Here is a function signature example:

class Solution: 

  def getRange(self, arr, target):

    # Fill this in.

  

# Test program 

arr = [1, 2, 2, 2, 2, 3, 4, 7, 8, 8] 

x = 2

print(Solution().getRange(arr, x))

# [1, 4]