code: def _update_from_field(
      target_datapoints: List[Dict],
      field: str,
      source_datapoints: Optional[List[Dict]] = None,
      source_field: Optional[str] = None,
  ):
      if source_datapoints is None:
          source_datapoints = target_datapoints
      if source_field is None:
          source_field = field
  
      if len(source_datapoints) != len(target_datapoints):
          raise IndexError(
              "Source and target datapoints must have the same length"
          )
  
      for index, datapoint in enumerate(target_datapoints):
          source_datapoint = source_datapoints[index]
          if source_field in source_datapoint:
              datapoint[field] = source_datapoint[source_field]
  
imports: import os
  from typing import Any, Dict, Iterable, List, Optional, Tuple, Union
  from funcy import first, last
  from dvc.exceptions import DvcException
  from dvc.render import FIELD, FILENAME, INDEX, REVISION
  from .None import Converter
label_desc: Use image node_id 10 for calling a global function with example usage: _update_from_field(target_datapoints, field, source_datapoints, source_field) without return types