Two Pointers: Inward Traversal

def pair_sum_sorted(nums: List[int], target: int) -> List[int]:
  left, right = 0, len(nums)-1
  while left < right:
    sums = nums[left] + nums[right]
    # if the sum is smaller, increment the left pointer, aiming 
    # to increase the sum towards the target value
    if sums < target:
      left += 1
    # if the sum is larger, decrement the right pointer, aiming 
    # to decrease the sum towards the target value
    elif sums > target:
      right -=1
    # If target pair is found return its indices 
    else: 
      return [left,right]
  return []