def _fdopen(self, *args, **kwargs):
        """Redirector to open() builtin function.

        Args:
            *args: Pass through args.
            **kwargs: Pass through kwargs.

        Returns:
            File object corresponding to file_des.

        Raises:
            TypeError: if file descriptor is not an integer.
        """
        if not is_int_type(args[0]):
            raise TypeError('an integer is required')
        return FakeFileOpen(self.filesystem)(*args, **kwargs)