def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
def __init__(self, parent, window):
		self._parent = parent
		self._window = window
		self._application = self._parent._application

		# create user interface
		self._container = gtk.VBox(False, 5)
		self._controls = gtk.HBox(False, 5)

		separator = gtk.HSeparator()

		# pack interface
		self._container.pack_end(separator, False, False, 0)
		self._container.pack_end(self._controls, False, False, 0)