code: def get_title(self, context_keys=()):
      return ("doc_index", "raw_input", "predictions", "targets")
  
imports: from typing import Dict, List
  import torch
  from pytext.common.constants import BatchContext, DatasetFieldName, RawExampleFieldName, Stage
  from pytext.data.tensorizers import Tensorizer
  from pytext.metric_reporters.channel import Channel, ConsoleChannel, FileChannel
  from pytext.metric_reporters.metric_reporter import MetricReporter
  from pytext.metrics import safe_division
  from pytext.metrics.seq2seq_metrics import compute_f1, Seq2SeqMetrics
label_desc: Use image node_id 2 for calling the Seq2SeqFileChannel obj's underlying member method code with example usage: obj.get_title(context_keys) and returns: str,  str,  str,  str