code: def is_graphviz_available():
      """Tell whether graphviz is available or not."""
      return is_return_code_zero(["dot", "-V"])
  
file_path: chainer/chainer/training/extensions/computational_graph.py
imports: import os
  import subprocess
  from chainer import computational_graph
  from chainer import configuration
  from chainer.training import extension
  from chainer.utils import argument
  from chainer import variable
label_desc: Use image node_id 2 for calling a global function with example usage: is_graphviz_available() and returns: is_return_code_zero