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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 _get_signing_jwk_key_set(jwt_issuer):
 """ Returns a JWK Keyset containing all active keys that are configured for verifying signatures. """

    key_set = KEYS()

    # asymmetric keys
    signing_jwk_set = settings.JWT_AUTH.get('JWT_PUBLIC_SIGNING_JWK_SET')
    if signing_jwk_set:
        key_set.load_jwks(signing_jwk_set)

    # symmetric key
    key_set.add({'key': jwt_issuer['SECRET_KEY'], 'kty': 'oct'})

    return key_set