def __init__(self, exiter, args=None, env=None):
    self._exiter = exiter
    self._args = args or sys.argv
    self._env = env or os.environ
Get a TreeWalker class for various types of tree with built-in support
dataset/ETHPy150Open pantsbuild/pants/src/python/pants/bin/pants_runner.py/PantsRunner.__init__--crossover with--dataset/ETHPy150Open html5lib/html5lib-python/html5lib/treewalkers/__init__.py/getTreeWalker