code: def get_xdg_dir():
      """Return the XDG_CONFIG_HOME, if it is defined and exists, else None.
  
      This is only for non-OS X posix (Linux,Unix,etc.) systems.
      """
  
      env = os.environ
  
      if os.name == "posix":
          # Linux, Unix, AIX, etc.
          # use ~/.config if empty OR not set
          xdg = env.get("XDG_CONFIG_HOME", None) or os.path.join(
              get_home_dir(), ".config"
          )
          if xdg and _writable_dir(xdg):
              assert isinstance(xdg, str)
              return xdg
  
      return None
  
imports: import os
  import sys
  import errno
  import shutil
  import random
  import glob
  from IPython.utils.process import system
label_desc: Use image node_id 7 for calling a global function with example usage: get_xdg_dir() and returns: None, xdg