function assertExistsimport { assertExists } from "https://deno.land/std@0.202.0/testing/asserts.ts"; assertExists<T>(actual: T, msg?: string): asserts actual is NonNullable<T>Make an assertion that actual is not null or undefined. If not then throw. Type ParametersTParametersactual: Toptionalmsg: stringReturnsasserts actual is NonNullable<T>