method Page.prototype.onceRe-exportimport { Page } from "https://deno.land/x/gfm@0.6.0/test/test_deps.ts"; once<K extends keyof PageEventObject>(eventName: K, handler: (event: PageEventObject[K]) => void): EventEmitterType ParametersK extends keyof PageEventObjectParameterseventName: Khandler: (event: PageEventObject[K]) => voidReturnsEventEmitter