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, path):
        """Similar to matcher.visitdir"""
        path = normalizerootdir(path, "visitdir")
        if self.matchrecursive:
            return "all"
        elif self.unsurerecursive:
            return True
        elif path == "":
            return True

        if self._kindpats and self._compiledpats(path):
            # XXX: This is incorrect. But re patterns are already used in
            # production. We should kill them!
            # Need to test "if every string starting with 'path' matches".
            # Obviously it's impossible to test *every* string with the
            # standard regex API, therefore pick a random strange path to test
            # it approximately.
            if self._compiledpats("%s/*/_/-/0/*" % path):
                return "all"
            else:
                return True

        if self._globdirpats and self._compileddirpats(path):
            return True

        subdir, rest = self._split(path)
        subtree = self.get(subdir)
        if subtree is None:
            return False
        else:
            return subtree.visitdir(rest)