code: def command_exists(command):
      which = "which"
      if platform.system() == "Windows":
          which = "where"
      retval = call([which, command])
      return not retval
  
file_path: nnabla/python/test/cpp/test_nbla.py
imports: import pytest
  import nnabla
  import nnabla.functions
  import nnabla.utils.save
  import nnabla.utils.load
  from nnabla.testing import assert_allclose
  import numpy
  from subprocess import check_call, call, check_output
  import platform
label_desc: Use image node_id 1 for calling a global function with example usage: command_exists(command) and returns: unknown