code: def test_float_size(self):
      x0 = np.array([2, 3, 4]).astype(np.float32)
  
      # check that ScalarFunction/approx_derivative always send the correct
      # float width
      def rosen_(x):
          assert x.dtype == np.float32
          return rosen(x)
  
      sf = ScalarFunction(
          rosen_, x0, (), "2-point", rosen_hess, None, (-np.inf, np.inf)
      )
      res = sf.fun(x0)
      assert res.dtype == np.float32
  
imports: import pytest
  import numpy
  from numpy.testing import TestCase, assert_array_almost_equal, assert_array_equal, assert_, assert_allclose, assert_equal
  from scipy.sparse import csr_matrix
  from scipy.sparse.linalg import LinearOperator
  from scipy.optimize._differentiable_functions import ScalarFunction, VectorFunction, LinearVectorFunction, IdentityVectorFunction
  from scipy.optimize import rosen, rosen_der, rosen_hess
  from scipy.optimize._hessian_update_strategy import BFGS
label_desc: Use image node_id 6 for calling the TestScalarFunction obj's underlying member method code with example usage: obj.test_float_size() and returns: rosen