code: def test_rmse(self):
      y = turicreate.SArray([1, 2, 1, 2])
      yhat = turicreate.SArray([3, -1, 1, 0])
      rmse = turicreate.toolkits.evaluation.rmse(y, yhat)
      true_rmse = (float(2 * 2 + 3 * 3 + 0 + 2 * 2) / 4) ** 0.5
      self.assertAlmostEqual(rmse, true_rmse)
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import turicreate
  from turicreate.toolkits._main import ToolkitError
  import math
  from numpy import inf
  import numpy
label_desc: Use image node_id 1 for calling the MetricsTest obj's underlying member method code with example usage: obj.test_rmse() without return types