code: func (k *KeyPairsClient) Create(ctx context.Context, pubKey *envelope.PublicKey,
  	privKey *envelope.PrivateKey, claim *envelope.Claim) (*envelope.PublicKey,
  	*envelope.PrivateKey, []envelope.Claim, error) {
  
  	req := ClaimedKeyPair{
  		PublicKeySegment: apitypes.PublicKeySegment{
  			PublicKey: pubKey,
  			Claims:    []envelope.Claim{*claim},
  		},
  		PrivateKey: privKey,
  	}
  	resp := ClaimedKeyPair{}
  	err := k.client.RoundTrip(ctx, "POST", "/keypairs", nil, &req, &resp)
  	if err != nil {
  		return nil, nil, nil, err
  	}
  
  	return resp.PublicKey, resp.PrivateKey, resp.Claims, nil
  }
docs: // Create creates a new keypair on the registry.
  //
  // The keypair includes the user's public key, private key, and a self-signed
  // claim on the public key.
  //
  // keys may be either signing or encryption keys.