def _iter_packed_refs(cls, repo: "Repo") -> Iterator[Tuple[str, str]]:
        """Return an iterator yielding pairs of sha1/path pairs (as strings) for the
        corresponding refs.

        :note:
            The packed refs file will be kept open as long as we iterate.
        """
        try:
            with open(cls._get_packed_refs_path(repo), "rt", encoding="UTF-8") as fp:
                for line in fp:
                    line = line.strip()
                    if not line:
                        continue
                    if line.startswith("#"):
                        # "# pack-refs with: peeled fully-peeled sorted"
                        # the git source code shows "peeled",
                        # "fully-peeled" and "sorted" as the keywords
                        # that can go on this line, as per comments in git file
                        # refs/packed-backend.c
                        # I looked at master on 2017-10-11,
                        # commit 111ef79afe, after tag v2.15.0-rc1
                        # from repo https://github.com/git/git.git
                        if line.startswith("# pack-refs with:") and "peeled" not in line:
                            raise TypeError("PackingType of packed-Refs not understood: %r" % line)
                        # END abort if we do not understand the packing scheme
                        continue
                    # END parse comment

                    # Skip dereferenced tag object entries - previous line was actual
                    # tag reference for it.
                    if line[0] == "^":
                        continue

                    yield cast(Tuple[str, str], tuple(line.split(" ", 1)))
                # END for each line
        except OSError:
            return None
        # END no packed-refs file handling
Return an iterator yielding pairs of sha1/path pairs (as strings) for the
        corresponding refs.

        :note:
            The packed refs file will be kept open as long as we iterate.
        
git/refs/symbolic.py