code: def test_schaffer2_output(common_minima):
      """Test schaffer2 function output."""
      assert np.isclose(fx.schaffer2(common_minima), np.zeros(3)).all()
  
imports: from collections import namedtuple
  import numpy
  import pytest
  from pyswarms.utils.functions import single_obj
label_desc: Use image node_id 15 for calling a global function with example usage: test_schaffer2_output(common_minima) without return types