Write a method that removes duplicate String values from a List while preserving the original order of first occurrences. The method should return a new List with unique values only.

Examples:

Input: ['apple', 'banana', 'apple', 'orange', 'banana'] Output: ['apple', 'banana', 'orange'] Explanation: Duplicates removed, first occurrence kept Input: ['hello', 'world', 'hello'] Output: ['hello', 'world'] Explanation: Second 'hello' is removed Input: ['a', 'b', 'c'] Output: ['a', 'b', 'c'] Explanation: No duplicates, list unchanged Input: [] Output: [] Explanation: Empty list remains empty
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