class_docstr: MetadataWriter to write the metadata into the object detector.
code: def populate(self) -> "tuple[bytearray, str]":
      model_buf, _ = super().populate()
      metadata_buf = metadata.get_metadata_buffer(model_buf)
      json_content = convert_to_json(metadata_buf)
      return model_buf, json_content
  
imports: import dataclasses
  from typing import List, Optional
  import flatbuffers
  from mediapipe.tasks.metadata import metadata_schema_py_generated
  from mediapipe.tasks.metadata import object_detector_metadata_schema_py_generated
  from mediapipe.tasks.python.metadata import metadata
  from mediapipe.tasks.python.metadata.metadata_writers import metadata_info
  from mediapipe.tasks.python.metadata.metadata_writers import metadata_writer
label_desc: Use image node_id 3 for calling the MetadataWriter obj's underlying member method code with example usage: obj.populate() and returns: model_buf,  json_content