def _get_unstack_items(self, unstacker, new_columns):
<EOL>new_items = unstacker.get_new_columns()<EOL>new_placement = new_columns.get_indexer(new_items)<EOL>new_values, mask = unstacker.get_new_values()<EOL>mask = mask.any(<NUM_LIT:0>)<EOL>return new_placement, new_values, mask<EOL>
Get the placement, values, and mask for a Block unstack.

This is shared between ObjectBlock and ExtensionBlock. They
differ in that ObjectBlock passes the values, while ExtensionBlock
passes the dummy ndarray of positions to be used by a take
later.

Parameters
----------
unstacker : pandas.core.reshape.reshape._Unstacker
new_columns : Index
    All columns of the unstacked BlockManager.

Returns
-------
new_placement : ndarray[int]
    The placement of the new columns in `new_columns`.
new_values : Union[ndarray, ExtensionArray]
    The first return value from _Unstacker.get_new_values.
mask : ndarray[bool]
    The second return value from _Unstacker.get_new_values.