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 visitdir(self, dir):
        m1dir = self.m1.visitdir(dir)
        m2dir = self.m2.visitdir(dir)

        # if both matchers return "all" then we know for sure we don't need
        # to visit this directory. Same if all matchers return False. In all
        # other case we have to visit a directory.
        if m1dir == "all" and m2dir == "all":
            return False
        if not m1dir and not m2dir:
            return False
        return True