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 _get_selected_path(self):
        """
        Helper function to get the selected path

        @return Gtk.TreePath : returns exactly one path for the selected object
                               or None
        """
        selection = self.get_selection()
        if selection:
            model, selected_paths = self.get_selection().get_selected_rows()
            if selected_paths:
                return selected_paths[0]
        return None