How to use the deal.linter._contract.Category function in deal

# add
    stub.add(func='fname', contract=Category.RAISES, value='TypeError')
    with pytest.raises(ValueError, match='unsupported contract'):
        stub.add(func='fname', contract=Category.POST, value='SyntaxError')
    assert stub._content == {'fname': {'raises': ['TypeError']}}

    # do not add twice
    stub.add(func='fname', contract=Category.RAISES, value='TypeError')
    assert stub._content == {'fname': {'raises': ['TypeError']}}

    # get
    assert stub.get(func='fname', contract=Category.RAISES) == frozenset({'TypeError'})
    with pytest.raises(ValueError, match='unsupported contract'):
        stub.get(func='fname', contract=Category.POST)
    assert stub.get(func='unknown', contract=Category.RAISES) == frozenset()

    # dump
    stub.dump()
    content = json.loads(path.read_text(encoding='utf8'))
    assert content == {'fname': {'raises': ['TypeError']}}

    # load
    stub2 = StubFile(path=path)
    stub2.load()
    assert stub2._content == {'fname': {'raises': ['TypeError']}}

def test_stub_file(tmp_path: Path):
    path = tmp_path / 'example.json'
    stub = StubFile(path=path)

    # add
    stub.add(func='fname', contract=Category.RAISES, value='TypeError')
    with pytest.raises(ValueError, match='unsupported contract'):
        stub.add(func='fname', contract=Category.POST, value='SyntaxError')
    assert stub._content == {'fname': {'raises': ['TypeError']}}

    # do not add twice
    stub.add(func='fname', contract=Category.RAISES, value='TypeError')
    assert stub._content == {'fname': {'raises': ['TypeError']}}

    # get
    assert stub.get(func='fname', contract=Category.RAISES) == frozenset({'TypeError'})
    with pytest.raises(ValueError, match='unsupported contract'):
        stub.get(func='fname', contract=Category.POST)
    assert stub.get(func='unknown', contract=Category.RAISES) == frozenset()

    # dump
    stub.dump()

def __call__(self, func: Func, stubs: StubsManager = None) -> Iterator[Error]:
        for contract in func.contracts:
            if contract.category != Category.RAISES:
                continue
            yield from self._check(func=func, contract=contract, stubs=stubs)

def get(self, func: str, contract: Category) -> FrozenSet[str]:
        if contract != Category.RAISES:
            raise ValueError('unsupported contract')
        values = self._content.get(func, {}).get(contract.value, [])
        return frozenset(values)

def add(self, func: str, contract: Category, value: str) -> None:
        if contract != Category.RAISES:
            raise ValueError('unsupported contract')
        contracts = self._content.setdefault(func, dict())
        values = contracts.setdefault(contract.value, [])
        if value in values:
            return
        values.append(value)
        values.sort()

def __call__(self, func: Func, stubs: StubsManager = None) -> Iterator[Error]:
        for contract in func.contracts:
            if contract.category != Category.POST:
                continue
            yield from self._check(func=func, contract=contract)

def from_astroid(cls, tree: astroid.Module) -> List['Func']:
        funcs = []
        for expr in tree.body:
            if not isinstance(expr, astroid.FunctionDef):
                continue
            contracts = []
            if expr.decorators:
                for category, args in get_contracts(expr.decorators.nodes):
                    contract = Contract(args=args, category=Category(category))
                    contracts.append(contract)
            funcs.append(cls(
                name=expr.name,
                body=expr.body,
                contracts=contracts,
                line=expr.lineno,
                col=expr.col_offset,
            ))
        return funcs

def __call__(self, func: Func, stubs: StubsManager = None) -> Iterator[Error]:
        for contract in func.contracts:
            if contract.category != Category.PURE:
                continue
            yield from self._check(func=func)
            return

def __call__(self, func: Func, stubs: StubsManager = None) -> Iterator[Error]:
        for contract in func.contracts:
            if contract.category != Category.SILENT:
                continue
            yield from self._check(func=func)
            # if `@deal.silent` is duplicated, check the function only once
            return

for func in infer(expr.func):
        if type(func) is not astroid.FunctionDef:
            continue
        if not func.decorators:
            continue
        code = 'def f({}):0'.format(func.args.as_string())
        func_args = ast.parse(code).body[0].args  # type: ignore

        for category, contract_args in get_contracts(func.decorators.nodes):
            if category != 'pre':
                continue

            contract = Contract(
                args=contract_args,
                category=Category.PRE,
                func_args=func_args,
            )
            try:
                result = contract.run(*args, **kwargs)
            except NameError:
                continue
            if result is False or type(result) is str:
                msg = _format_message(args, kwargs)
                yield Token(value=msg, line=expr.lineno, col=expr.col_offset)