function mock.returnsArgimport { mock } from "https://deno.land/x/deno_slack_sdk@1.5.0/dev_deps.ts"; const { returnsArg } = mock; returnsArg<Arg, Self = any>(idx: number): (this: Self, ...args: Arg[]) => ArgCreates a function that returns one of its arguments. Type ParametersArgoptionalSelf = anyParametersidx: numberReturns(this: Self, ...args: Arg[]) => Arg