code: def _get_afilter_desc(
      sample_rate: Optional[int],
      fmt: Optional[str],
      num_channels: Optional[int],
  ):
      descs = []
      if sample_rate is not None:
          descs.append(f"aresample={sample_rate}")
      if fmt is not None or num_channels is not None:
          parts = []
          if fmt is not None:
              parts.append(f"sample_fmts={fmt}")
          if num_channels is not None:
              parts.append(f"channel_layouts={num_channels}c")
          descs.append(f"aformat={':'.join(parts)}")
      return ",".join(descs) if descs else None
  
imports: from __future__ import annotations
  import os
  from dataclasses import dataclass
  from pathlib import Path
  from typing import BinaryIO, Dict, Iterator, Optional, Tuple, TypeVar, Union
  import torch
  import torio
  from torch.utils._pytree import tree_map
label_desc: Use image node_id 3 for calling a global function with example usage: _get_afilter_desc(sample_rate, fmt, num_channels) and returns: unknown