code: def rand_str(nchars: int) -> str:
      """
      Generate one random byte string.
      """
      RANDS_CHARS = np.array(
          list(string.ascii_letters + string.digits), dtype=(np.str_, 1)
      )
      return "".join(
          np.random.default_rng(2).choice(RANDS_CHARS, nchars)
      )
  
imports: from datetime import datetime, timedelta
  from importlib import reload
  import string
  import sys
  import numpy
  import pytest
  from pandas._libs.tslibs import iNaT
  import pandas.util._test_decorators
  from pandas import NA, Categorical, CategoricalDtype, DatetimeTZDtype, Index, Interval, NaT, Series, Timedelta, Timestamp, cut, date_range, to_datetime
  import pandas._testing
label_desc: Use image node_id 1 for calling a global function with example usage: rand_str(nchars) and returns: str