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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def refs_to(cls, sha1, repo):
 """Returns all refs pointing to the given SHA1."""

        matching = []
        for refname in repo.listall_references():
            symref = repo.lookup_reference(refname)
            dref = symref.resolve()
            oid = dref.target
            commit = repo.get(oid)
            if commit.hex == sha1:
                matching.append(symref.shorthand)

        return matching