Find whether the files on the left and right are different. Note,
        modified implies the contents of the file have changed, which is
        predicated on the file existing on both the left and right. Therefore
        this will be false if the file on the left has been deleted, or the
        file on the right is new.

        :return: Whether the file has been modified.

def is_modified(self) -> bool:
        """
        Find whether the files on the left and right are different. Note,
        modified implies the contents of the file have changed, which is
        predicated on the file existing on both the left and right. Therefore
        this will be false if the file on the left has been deleted, or the
        file on the right is new.

        :return: Whether the file has been modified.
        """
        if self.is_new or self.is_deleted:
            return False
        return self.left.md5 != self.right.md5