def METHOD_NAME(rec, seen):
    conditionSet = []
    conditionSets = (
        rec.ConditionSet.ConditionTable if rec.ConditionSet is not None else []
    )
    for cond in conditionSets:
        if cond.Format != 1:
            # can't tell whether this is duplicate, assume is unique
            return True
        conditionSet.append(
            (cond.AxisIndex, cond.FilterRangeMinValue, cond.FilterRangeMaxValue)
        )
    # besides the set of conditions, we also include the FeatureTableSubstitution
    # version to identify unique FeatureVariationRecords, even though only one
    # version is currently defined. It's theoretically possible that multiple
    # records with same conditions but different substitution table version be
    # present in the same font for backward compatibility.
    recordKey = frozenset([rec.FeatureTableSubstitution.Version] + conditionSet)
    if recordKey in seen:
        return False
    else:
        seen.add(recordKey)  # side effect
        return True