Extract unique elements while keeping order

Summary

Return a list of the first occurrence of each element while preserving original order.

Problem statement

Create a function unique_preserve_order(items) that takes a list and returns a new list containing only the first occurrence of each element, preserving the original order. Assume elements are hashable. Example: [1,2,1,3,2] -> [1,2,3].

Task

Implement a function that returns unique items from a list in the order they first appear.

Examples

Input format

A single list of hashable elements (numbers, strings, tuples, etc.).

Output format

A list with duplicates removed, preserving the first occurrence order.

Constraints

Elements are hashable. Input length up to a few thousand elements.

Samples