code: def onlyif_cmds_exist(*commands):
      """
      Decorator to skip test when at least one of `commands` is not found.
      """
      for cmd in commands:
          if not which(cmd):
              return skip(
                  "This test runs only if command '{0}' "
                  "is installed".format(cmd)
              )
      return null_deco
  
file_path: catboost/contrib/python/ipython/py2/IPython/testing/decorators.py
imports: import sys
  import os
  import tempfile
  import unittest
  import warnings
  from decorator import decorator
  from .ipunittest import ipdoctest, ipdocstring
  from IPython.external.decorators import *
  from IPython.utils.py3compat import string_types, which, PY2, PY3, PYPY
label_desc: Use image node_id 10 for calling a global function with example usage: onlyif_cmds_exist() and returns: null_deco, skip