code: def test_var(self):
      for varname, expected in self.variances.items():
          samples = self.samples[varname]
          npt.assert_allclose(
              expected, samples.var(0), self.rtol, self.atol
          )
  
imports: import arviz
  import numpy
  import numpy.testing
  import pytensor.tensor
  from scipy import stats
  import pymc
  from pymc.backends.arviz import to_inference_data
  from pymc.util import get_var_name
label_desc: Use image node_id 1 for calling the KnownVariance obj's underlying member method code with example usage: obj.test_var() without return types