def METHOD_NAME(self):
    min = self.pyx
    for em in [
        ["forsterite", "fayalite"],
        ["enstatite", "ferrosilite"],
        [
            pt.formula("SiO2"),
            pt.formula("MgO"),
            ("iron oxide", pt.formula("Fe2O3")),
        ],
    ]:
        min.set_endmembers(em)
        self.assertTrue(min.endmembers != {})