def Item(self, key):<EOL>
return self._compose_optic(optics.ItemLens(key))<EOL>
A lens that focuses a single item (key-value pair) in a
        dictionary by its key. Set an item to `None` to remove it from
        the dictionary.

            >>> from lenses import lens
            >>> from collections import OrderedDict
            >>> data = OrderedDict([(1, 10), (2, 20)])
            >>> lens.Item(1)
            UnboundLens(ItemLens(1))
            >>> lens.Item(1).get()(data)
            (1, 10)
            >>> lens.Item(3).get()(data) is None
            True
            >>> lens.Item(1).set((1, 11))(data)
            OrderedDict([(1, 11), (2, 20)])
            >>> lens.Item(1).set(None)(data)
            OrderedDict([(2, 20)])