How to search particular material with fixed no of Oxygen atoms?

I want to search all material that contain 8 oxygen atoms. For example Li3Cu4TeO8 has 8 oxygen atoms. How to get all materials?

You can use the MPRester query with the following criteria={"unit_cell_formula.O": 8} for specifying that 8 atoms must be in the unit cell or reduced_cell_formula for specifying that 8 oxygens are present in the reduced formula.