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 should return 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.