class_docstr: OSS Filesystem Tests
code: def test_append(self):
      file_path = file_io.join(self._base_dir, "temp_file")
      with self.assertRaises(errors.UnimplementedError):
          with gfile.Open(file_path, mode="a") as f:
              f.write("a1\n")
  
imports: import os
  import unittest
  from tensorflow.python.framework import errors
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.platform import test
  from tensorflow.python.platform import gfile
  import tensorflow
  import tensorflow_io
label_desc: Use image node_id 9 for calling the OSSFSTest obj's underlying member method code with example usage: obj.test_append() without return types