``unique_values`` for string dtypes may return unsorted data
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np.unique now supports hash‐based duplicate removal for string dtypes.
This enhancement extends the hash-table algorithm to byte strings ('S'),
Unicode strings ('U'), and the experimental string dtype ('T', StringDType).
As a result, calling np.unique() on an array of strings will use
the faster hash-based method to obtain unique values.
Note that this hash-based method does not guarantee that the returned unique values will be sorted.
This also works for StringDType arrays containing None (missing values)
when using equal_nan=True (treating missing values as equal).