code: def _format_prerequisites_attrs(data_arr: xr.DataArray) -> None:
      """Reformat prerequisites attribute value to string."""
      if "prerequisites" in data_arr.attrs:
          data_arr.attrs["prerequisites"] = [
              np.bytes_(str(prereq))
              for prereq in data_arr.attrs["prerequisites"]
          ]
  
imports: from __future__ import annotations
  import datetime
  import json
  import logging
  from collections import OrderedDict
  import numpy
  import xarray
  from satpy.writers.utils import flatten_dict
label_desc: Use image node_id 12 for calling a global function with example usage: _format_prerequisites_attrs(data_arr) without return types