code: def test_find_reasonable_stepsize(self):
      np.random.seed(987654321)
      stepsize = self.hmc_sampler._find_reasonable_stepsize(
          np.array([-1, 1, -1])
      )
      np.testing.assert_almost_equal(stepsize, 2.0)
  
imports: import sys
  import unittest
  import numpy
  from pgmpy.factors.distributions import GaussianDistribution
  from pgmpy.sampling import HamiltonianMC, HamiltonianMCDA, GradLogPDFGaussian, NoUTurnSampler, NoUTurnSamplerDA
label_desc: Use image node_id 4 for calling the TestHMCInference obj's underlying member method code with example usage: obj.test_find_reasonable_stepsize() without return types