Cognite Data Fusion can expose large collections of numeric telemetry readings. Given a list of integer readings and a target value, return every distinct unordered pair of values whose sum equals the target.
Each pair must be represented as [smaller, larger], including pairs containing the same value, such as [3, 3]. Return the pairs sorted lexicographically. Duplicate readings must not create duplicate pairs.
Implement a function that accepts nums, a list of integers, and target, an integer. Return a list of two-element integer lists. Every returned pair [a, b] must satisfy a <= b and a + b == target. Return [] when no valid pair exists.
def distinct_sum_pairs(nums, target):