code: def test_smooth_1():
      G = basic_graph()
      field = np.zeros((1000, 1))
      field[555, 0] = 1
      G.set_field(field)
      G.diffusion()
      sfield = G.get_field()
      assert sfield[555] == 0
      assert sfield[554] == 1
      assert np.abs(sfield[566] - np.sqrt(2)) < 1.0e-7
      assert np.abs(sfield[446] - np.sqrt(3)) < 1.0e-7
  
imports: import numpy
  import numpy.random
  from numpy.testing import assert_array_equal
  from ..field import field_from_coo_matrix_and_data, field_from_graph_and_data
  from ..graph import wgraph_from_3d_grid
label_desc: Use image node_id 11 for calling a global function with example usage: test_smooth_1() without return types