'The a native Python datatype representation of this value
:return:
If a _map is set, a set of names, or if no _map is set, a tuple of
integers 1 and 0. None if no value.'

@property
def native(self):

    if (self.contents is None):
        if (self._map is None):
            self.set(())
        else:
            self.set(set())
    if (self._native is None):
        bits = self._merge_chunks()
        if self._map:
            self._native = set()
            for (index, bit) in enumerate(bits):
                if bit:
                    name = self._map.get(index, index)
                    self._native.add(name)
        else:
            self._native = bits
    return self._native
