CompletedTask object.
https://docs.dataforseo.com/v2/srp#setting-serp-tasks
t() :: %DataForSeo.Serp.CompletedTask{ key_id: term(), loc_id: term(), post_id: term(), post_key: term(), result_extra: term(), result_se_check_url: term(), result_spell: term(), result_spell_type: term(), results_count: term(), se_id: term(), task_id: term() }