def METHOD_NAME(mocker, mongodb_obj):
    # Arrange
    mock_collection = mocker.MagicMock()
    mock_collection.collection_type.return_value = "distro"
    mock_serialize_item = mocker.patch.object(mongodb_obj, "serialize_item")
    mock_collection.__iter__ = mocker.Mock(return_value=iter(["item1"]))
    # Act
    mongodb_obj.serialize(mock_collection)
    # Assert
    assert mock_serialize_item.call_count == 1