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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 verify( signature: Ed25519Signature, digest: bytes, pub_key: Ed25519PublicPoint ) -> None: """Verify Ed25519 signature. Raise exception if the signature is invalid."""

    # XXX this *might* change to bool function
    _ed25519.checkvalid(signature, digest, pub_key)