code: def test_flatten_2d(dummy: ep.Tensor) -> None:
      x = ep.zeros(dummy, (4, 5))
      x = fbn.devutils.flatten(x)
      assert x.shape == (4, 5)
  
imports: import pytest
  import foolbox
  import eagerpy
label_desc: Use image node_id 3 for calling a global function with example usage: test_flatten_2d(dummy) without return types