code: def test_request_header_context_provider_registry_register():
      provider_class = mock.Mock()
  
      registry = RequestHeaderProviderRegistry()
      registry.register(provider_class)
  
      assert set(registry) == {provider_class.return_value}
  
file_path: mlflow/tests/tracking/request_header/test_registry.py
imports: from importlib import reload
  from unittest import mock
  import pytest
  import mlflow.tracking.request_header.registry
  from mlflow.tracking.request_header.databricks_request_header_provider import DatabricksRequestHeaderProvider
  from mlflow.tracking.request_header.registry import RequestHeaderProviderRegistry, resolve_request_headers
label_desc: Use image node_id 2 for calling a global function with example usage: test_request_header_context_provider_registry_register() without return types