def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def _reset_exiter(cls, exiter: Optional[Exiter]) -> None:
        """Class state:

        - Overwrites `cls._exiter`.
        Python state:
        - Overwrites sys.excepthook.
        """
        logger.debug(f"overriding the global exiter with {exiter} (from {cls._exiter})")
        # NB: mutate the class variables! This is done before mutating the exception hook, because the
        # uncaught exception handler uses cls._exiter to exit.
        cls._exiter = exiter
        # NB: mutate process-global state!
        sys.excepthook = cls._log_unhandled_exception_and_exit