get_preset: RuntimeDescriptor<[id: string | undefined], Binary | undefined>

Returns a JSON blob representation of the built-in RuntimeGenesisConfig identified by id.

If id is None the function returns JSON blob representation of the default RuntimeGenesisConfig struct of the runtime. Implementation must provide default RuntimeGenesisConfig.

Otherwise function returns a JSON representation of the built-in, named RuntimeGenesisConfig preset identified by id, or None if such preset does not exist. Returned Vec<u8> contains bytes of JSON blob (patch) which comprises a list of (potentially nested) key-value pairs that are intended for customizing the default runtime genesis config. The patch shall be merged (rfc7386) with the JSON representation of the default RuntimeGenesisConfig to create a comprehensive genesis config that can be used in build_state method.