ConstructionPreprocessResponse : ConstructionPreprocessResponse contains options that will be sent unmodified to /construction/metadata. If it is not necessary to make a request to /construction/metadata, options should be omitted. Some blockchains require the PublicKey of particular AccountIdentifiers to construct a valid transaction. To fetch these PublicKeys, populate required_public_keys with the AccountIdentifiers associated with the desired PublicKeys. If it is not necessary to retrieve any PublicKeys for construction, required_public_keys should be omitted.