code: def test_astype_to_string_not_modifying_input(string_storage, val):
      # GH#51073
      df = DataFrame({"a": ["a", "b", val]})
      expected = df.copy()
      with option_context("mode.string_storage", string_storage):
          df.astype("string", copy=False)
      tm.assert_frame_equal(df, expected)
  
imports: import re
  import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import Categorical, CategoricalDtype, DataFrame, DatetimeTZDtype, Index, Interval, IntervalDtype, NaT, Series, Timedelta, Timestamp, concat, date_range, option_context
  import pandas._testing
label_desc: Use image node_id 4 for calling a global function with example usage: test_astype_to_string_not_modifying_input(string_storage, val) without return types