def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def setUp(self):
        entry_Li = ComputedEntry("Li", -1.90753119)

        with open(os.path.join(PymatgenTest.TEST_FILES_DIR, "LiTiO2_batt.json")) as f:
            entries_LTO = json.load(f, cls=MontyDecoder)
            self.ie_LTO = InsertionElectrode.from_entries(entries_LTO, entry_Li)

        with open(os.path.join(PymatgenTest.TEST_FILES_DIR, "FeF3_batt.json")) as fid:
            entries = json.load(fid, cls=MontyDecoder)
            self.ce_FF = ConversionElectrode.from_composition_and_entries(Composition("FeF3"), entries)