code: def testExistence(self):
      self.assertIsInstance(
          gfile.get_filesystem(
              "simplecache::nonexistent::file://blah/blah"
          ),
          gfile.FSSpecFileSystem,
      )
  
imports: import posixpath
  from tensorboard import test
  from tensorboard.compat.tensorflow_stub import errors
  from tensorboard.compat.tensorflow_stub.io import gfile
  import fsspec
label_desc: Use image node_id 22 for calling the GFileFSSpecTest obj's underlying member method code with example usage: obj.testExistence() without return types