code: def test_unary_op(self, func_name, a, expected, atol):
      gs_fnc = get_backend_fnc(func_name)
      res = gs_fnc(a)
      self.assertAllClose(res, expected, atol)
  
imports: import random
  import numpy
  import pytest
  import scipy
  import geomstats.backend
  from geomstats.test.test_case import TestCase
  from geomstats.test.vectorization import generate_vectorization_data
label_desc: Use image node_id 2 for calling the BackendTestCase obj's underlying member method code with example usage: obj.test_unary_op(func_name, a, expected, atol) without return types