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 flush_to_index(self) -> None:
        """Flush changes in our configuration file to the index"""
        assert self._smref is not None
        # should always have a file here
        assert not isinstance(self._file_or_files, BytesIO)

        sm = self._smref()
        if sm is not None:
            index = self._index
            if index is None:
                index = sm.repo.index
            # END handle index
            index.add([sm.k_modules_file], write=self._auto_write)
            sm._clear_cache()
        # END handle weakref