def METHOD_NAME(unbounded_condition):
    """Check that split functions can handle conditions that are partially
    unbounded without tripping over None values and missing keys."""
    doc = DesignSpaceDocument()
    doc.addAxisDescriptor(
        name="Weight", tag="wght", minimum=400, maximum=1000, default=400
    )
    doc.addRuleDescriptor(
        name="unbounded",
        conditionSets=[[unbounded_condition]],
    )
    assert len(list(splitInterpolable(doc))) == 1
    assert len(list(splitVariableFonts(doc))) == 1