function returnsArgimport { returnsArg } from "https://deno.land/std@0.202.0/testing/mock.ts"; 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