code: def validate_fairseq_dataset_exists(prefix):
      if not PathManager.exists(f"{prefix}.idx"):
          raise ValueError(f"{prefix}.idx not found!")
      if not PathManager.exists(f"{prefix}.bin"):
          raise ValueError(f"{prefix}.bin not found!")
  
imports: from typing import Optional
  from fvcore.common.file_io import PathManager
  from pytorch_translate.data import char_data, data, weighted_data
label_desc: Use image node_id 3 for calling a global function with example usage: validate_fairseq_dataset_exists(prefix) without return types