def METHOD_NAME(value, inputUnit, outputUnit):
    if inputUnit is outputUnit:
        return value
    if value is None:
        return None
    if _converters is None:
        _initConverters()
    converter = _converters.get((inputUnit, outputUnit), None)
    if converter is None:
        raise TypeError("Impossible to convert from %s to %s" % (inputUnit.name, outputUnit.name))
    return converter(value)