_mean raises TypeError on a score list containing None, unlike _stdev and _pstdev

[sclfcz]

What happened

_mean in unstructured/metrics/utils.py documents "Returns None if no element in the list", but unlike its neighbours _stdev and _pstdev it does not drop None values before averaging:

def _mean(scores: Union[pd.Series, List[float]], rounding: Optional[int] = 3):
    if len(scores) == 0:
        return None
    mean = statistics.mean(scores)      # TypeError on a None entry

from unstructured.metrics.utils import _mean, _stdev, _pstdev
_mean([0.9, None, 0.8])     # TypeError: can't convert type 'NoneType' to numerator/denominator
_stdev([0.9, None, 0.8])    # 0.071   (filters None, type hint is List[Optional[float]])
_pstdev([0.9, None, 0.8])   # 0.05    (same)

An unmeasured score is not a score, and the two sibling helpers already treat it that way — including in their type hints (List[Optional[float]]).

Expected

_mean should ignore None entries the same way, and return None when nothing is left to average.

Version

unstructured on main, Python 3.13.