code: def test_flatten_dict(self):
      # Valid types according to https://github.com/tensorflow/tensorboard/blob/1204566da5437af55109f7a4af18f9f8b7c4f864/tensorboard/plugins/hparams/summary_v2.py
      input_hparams = {
          # Example Invalid Types
          "None": None,
          "List": [1, 2, 3],
          "Tuple": (1, 2, 3),
          "Complex": complex("1+1j"),
          "np.complex_": np.complex_("1+1j"),
          # Valid Python Types
          "Bool": True,
          "Int": 1,
          "Float": 1.0,
          "Str": "test",
          # Valid Numpy Types
          "np.bool_": np.bool_(1),
          "np.integer": np.int_(1),
          "np.floating": np.float_(1.0),
          "np.character": np.str_("test"),
          # Nested dict to flatten
          "Nested_Dict": {
              "None": None,
              "List": [1, 2, 3],
              "Tuple": (1, 2, 3),
              "Complex": complex("1+1j"),
              "np.complex_": np.complex_("1+1j"),
              "Bool": True,
              "Int": 1,
              "Float": 1.0,
              "Str": "test",
              "np.bool_": np.bool_(1),
              "np.integer": np.int_(1),
              "np.floating": np.float_(1.0),
              "np.character": np.str_("test"),
          },
      }
  
      result_hparams = _flatten_dict(input_hparams)
  
      expected_hparams = {
          "None": "None",
          "List": "[1, 2, 3]",
          "Tuple": "(1, 2, 3)",
          "Complex": "(1+1j)",
          "np.complex_": "(1+1j)",
          # Valid Python Types
          "Bool": True,
          "Int": 1,
          "Float": 1.0,
          "Str": "test",
          # Valid Numpy Types
          "np.bool_": np.bool_(1),
          "np.integer": np.int_(1),
          "np.floating": np.float_(1.0),
          "np.character": np.str_("test"),
          # Nested Dict
          "Nested_Dict.None": "None",
          "Nested_Dict.List": "[1, 2, 3]",
          "Nested_Dict.Tuple": "(1, 2, 3)",
          "Nested_Dict.Complex": "(1+1j)",
          "Nested_Dict.np.complex_": "(1+1j)",
          "Nested_Dict.Bool": True,
          "Nested_Dict.Int": 1,
          "Nested_Dict.Float": 1.0,
          "Nested_Dict.Str": "test",
          "Nested_Dict.np.bool_": np.bool_(1),
          "Nested_Dict.np.integer": np.int_(1),
          "Nested_Dict.np.floating": np.float_(1.0),
          "Nested_Dict.np.character": np.str_("test"),
      }
  
      self.assertDictEqual(result_hparams, expected_hparams)
  
imports: import itertools
  import pathlib
  import tempfile
  import numpy
  import tensorflow
  from absl.testing import absltest
  from tensorboard.backend.event_processing import directory_watcher, event_file_loader
  from tensorboard.util import tensor_util
  from flax.metrics.tensorboard import SummaryWriter, _flatten_dict
label_desc: Use image node_id 16 for calling the TensorboardTest obj's underlying member method code with example usage: obj.test_flatten_dict() without return types