class_docstr: Base class to describe a dataset to be used with Implicitron.
  
  The dataset is made up of frames, and the frames are grouped into sequences.
  Each sequence has a name (a string).
  (A sequence could be a video, or a set of images of one scene.)
  
  This means they have a __getitem__ which returns an instance of a FrameData,
  which will describe one frame in one sequence.
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docstr: If the sequences in the dataset are videos rather than
  unordered views, then the dataset should override this method to
  return the index and timestamp in their videos of the frames whose
  indices are given in `idxs`. In addition,
  the values in _seq_to_idx should be in ascending order.
  If timestamps are absent, they should be replaced with a constant.
  
  This is used for letting SceneBatchSampler identify consecutive
  frames.
  
  Args:
      idxs: frame index in self
      subset_filter: If given, an index in idxs is ignored if the
          corresponding frame is not in any of the named subsets.
  
  Returns:
      tuple of
          - frame index in video
          - timestamp of frame in video
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code: def get_frame_numbers_and_timestamps(
      self,
      idxs: Sequence[int],
      subset_filter: Optional[Sequence[str]] = None,
  ) -> List[Tuple[int, float]]:
      """
      If the sequences in the dataset are videos rather than
      unordered views, then the dataset should override this method to
      return the index and timestamp in their videos of the frames whose
      indices are given in `idxs`. In addition,
      the values in _seq_to_idx should be in ascending order.
      If timestamps are absent, they should be replaced with a constant.
  
      This is used for letting SceneBatchSampler identify consecutive
      frames.
  
      Args:
          idxs: frame index in self
          subset_filter: If given, an index in idxs is ignored if the
              corresponding frame is not in any of the named subsets.
  
      Returns:
          tuple of
              - frame index in video
              - timestamp of frame in video
      """
      raise ValueError("This dataset does not contain videos.")
  
file_path: pytorch3d/pytorch3d/implicitron/dataset/dataset_base.py
imports: from collections import defaultdict
  from dataclasses import dataclass
  from typing import ClassVar, Dict, Iterable, Iterator, List, Optional, Sequence, Tuple, Type
  import torch
  from pytorch3d.implicitron.dataset.frame_data import FrameData
  from pytorch3d.implicitron.dataset.utils import GenericWorkaround
label_desc: Use image node_id 2 for calling the DatasetBase obj's underlying member method code with example usage: obj.get_frame_numbers_and_timestamps(idxs, subset_filter) without return types