code: def unsetenv(key):
      
  
      key = path2fsn(key)
      if is_win:
          # python 3 has no unsetenv under Windows -> use our ctypes one as well
          try:
              del_windows_env_var(key)
          except WindowsError:
              pass
      else:
          os.unsetenv(key)
docs: Like `os.unsetenv` but takes unicode under Windows + Python 2
  
      Args:
          key (pathlike): The env var to unset