code: def test_euler7():
      f = np.arange(100)
      f = (f % 5) == 1
      f = f.reshape((10, 10))
      with pytest.raises(ValueError):
          euler(f, 7)
  
imports: import numpy
  from mahotas.euler import euler, _euler_lookup4, _euler_lookup8
  import pytest
label_desc: Use image node_id 3 for calling a global function with example usage: test_euler7() without return types