import { collectFields } from "https://deno.land/x/graphql_deno@v15.0.0/lib/execution/execute.js";
Given a selectionSet, adds all of the fields in that selection to the passed in map of fields, and returns it at the end.
CollectFields requires the "runtime type" of an object. For a field which returns an Interface or Union type, the "runtime type" will be the actual Object type returned by that field.