code: def __init__(
      self,
      ann_file: str,
      topk: int = 10000,
      format_only: bool = False,
      outfile_prefix: Optional[str] = None,
      collect_device: str = "cpu",
      prefix: Optional[str] = None,
      backend_args: dict = None,
  ) -> None:
      if lvis is None:
          raise RuntimeError(
              'Package lvis is not installed. Please run "pip install '
              'git+https://github.com/lvis-dataset/lvis-api.git".'
          )
      super().__init__(collect_device=collect_device, prefix=prefix)
  
      self.format_only = format_only
      if self.format_only:
          assert (
              outfile_prefix is not None
          ), "outfile_prefix must be not"
          "None when format_only is True, otherwise the result files will"
          "be saved to a temp directory which will be cleaned up at the end."
  
      self.outfile_prefix = outfile_prefix
      self.backend_args = backend_args
  
      with get_local_path(
          ann_file, backend_args=self.backend_args
      ) as local_path:
          self._lvis_api = LVIS(local_path)
  
      self.cat_ids = self._lvis_api.get_cat_ids()
  
      self.results = {}
      self.topk = topk
  
imports: import itertools
  import logging
  import os.path
  import tempfile
  import warnings
  from collections import OrderedDict, defaultdict
  from typing import Dict, List, Optional, Sequence, Union
  import numpy
  import torch
  from mmengine.dist import all_gather_object, broadcast_object_list, is_main_process
  from mmengine.evaluator import BaseMetric
  from mmengine.evaluator.metric import _to_cpu
  from mmengine.fileio import get_local_path
  from mmengine.logging import MMLogger, print_log
  from terminaltables import AsciiTable
  from mmdet.registry import METRICS
  from mmdet.structures.mask import encode_mask_results
  from ..functional import eval_recalls
  from .coco_metric import CocoMetric
label_desc: Use image node_id 1 to create a new LVISFixedAPMetric object from inherited base classes: BaseMetric with example: obj = LVISFixedAPMetric(ann_file, topk, format_only, outfile_prefix, collect_device, prefix, backend_args)