function getHeaderimport { getHeader } from "https://deno.land/x/polkadot@0.2.11/api-derive/chain/index.ts"; getHeader(instanceId: string, api: DeriveApi): (blockHash: Uint8Array | string) => Observable<HeaderExtended>Examples const { author, number } = await api.derive.chain.getHeader('0x123...456'); console.log(`block #${number} was authored by ${author}`); ParametersinstanceId: string A block hash as U8 array or string. api: DeriveApiReturns(blockHash: Uint8Array | string) => Observable<HeaderExtended>An array containing the block header and the block author