code: func Seal(version Version, plaintext []byte, sender BoxSecretKey, receivers []BoxPublicKey) (out []byte, err error) {
  	ephemeralKeyCreator, err := receiversToEphemeralKeyCreator(receivers)
  	if err != nil {
  		return nil, err
  	}
  	return seal(version, plaintext, sender, receivers, ephemeralKeyCreator, defaultEncryptRNG{})
  }
docs: // Seal a plaintext from the given sender, for the specified receiver groups.
  // Returns a ciphertext, or an error if something bad happened.