code: def test_packed_batch():
      data = TestDataset()
      loader = PackedBatchLoader(
          data, batch_size=batch_size, epochs=1, shuffle=False
      )
      batches = list(loader)
  
      (x, a, e), y = batches[-1]
      n = max(ns)
      assert x.shape == (graphs_in_batch, n, f)
      assert a.shape == (graphs_in_batch, n, n)
      assert e.shape == (graphs_in_batch, n, n, s)
      assert y.shape == (graphs_in_batch, 2)
      assert loader.steps_per_epoch == np.ceil(len(data) / batch_size)
  
      signature = loader.tf_signature()
      assert len(signature[0]) == 3
  
imports: import numpy
  import scipy.sparse
  from spektral.data import BatchLoader, DisjointLoader
  from spektral.data.dataset import Dataset
  from spektral.data.graph import Graph
  from spektral.data.loaders import MixedLoader, PackedBatchLoader, SingleLoader
label_desc: Use image node_id 5 for calling a global function with example usage: test_packed_batch() without return types