code: def test_build_a_simple_data_loader():
      def call_fn(keys):
          return Promise.resolve(keys)
  
      identity_loader = DataLoader(call_fn)
  
      promise1 = identity_loader.load(1)
      assert isinstance(promise1, Promise)
  
      value1 = promise1.get()
      assert value1 == 1
  
imports: from pytest import raises
  from promise import Promise, async_instance
  from promise.dataloader import DataLoader
label_desc: Use image node_id 2 for calling a global function with example usage: test_build_a_simple_data_loader() and returns: Promise