code: def test_basic_stringlength(self, obj):
      length = len(str(obj))
      expected = np.dtype(f"S{length}")
  
      assert np.array(obj, dtype="S").dtype == expected
      assert np.array([obj], dtype="S").dtype == expected
  
      # A nested array is also discovered correctly
      arr = np.array(obj, dtype="O")
      assert np.array(arr, dtype="S").dtype == expected
      # Also if we use the dtype class
      assert np.array(arr, dtype=type(expected)).dtype == expected
      # Check that .astype() behaves identical
      assert arr.astype("S").dtype == expected
      # The DType class is accepted by `.astype()`
      assert arr.astype(type(np.dtype("S"))).dtype == expected
  
imports: from itertools import permutations, product
  import pytest
  from pytest import param
  import numpy
  from numpy.core._rational_tests import rational
  from numpy.core._multiarray_umath import _discover_array_parameters
  from numpy.testing import assert_array_equal, assert_warns, IS_PYPY
label_desc: Use image node_id 1 for calling the TestStringDiscovery obj's underlying member method code with example usage: obj.test_basic_stringlength(obj) without return types