code: def test_root():
      """test the isroot() method"""
      root = simple_forest().isroot()
      assert root[4] == True
      assert root.sum() == 1
  
file_path: nipy/nipy/algorithms/graph/tests/test_forest.py
imports: import numpy
  from ..forest import Forest
label_desc: Use image node_id 6 for calling a global function with example usage: test_root() without return types