Find two numbers that equal to target value
Few suggestions:

Naming: array is not an array, a more appropriate name can be numbers. Also unique_number_set can be just unique_numbers, the name already tells that there are no duplicates.
Unnecessary else: the else is not required so it can be removed.
Type hints: @Linny already pointed this out. I add that, if the result doesn't need to be modified, consider returning a tuple. Additionally, it tells the caller that the result will only contain two numbers.

from typing import List, Tuple, Union

def two_number_sum(numbers: List[int], target: int) -&gt; Union[Tuple[int, int], Tuple[()]]:
    unique_numbers = set()
    for num in numbers:
        required_value = target - num
        if required_value in unique_numbers:
            return num, required_value
        unique_numbers.add(num)
    return ()

Thanks to @KellyBundy and @AJNeufeld for the feedbacks in the comments.