class_docstr: Unit test class for testing scikit-learn converter.
code: def test_conversion_bad_inputs(self):
      # Error on converting an untrained model
      with self.assertRaises(Exception):
          model = Imputer()
          spec = converter.convert(model, "data", "out")
  
      # Check the expected class during covnersion.
      with self.assertRaises(Exception):
          from sklearn.linear_model import LinearRegression
  
          model = LinearRegression()
          spec = converter.convert(model, "data", "out")
  
imports: import unittest
  import numpy
  from coremltools._deps import _HAS_SKLEARN
label_desc: Use image node_id 3 for calling the ImputerTestCase obj's underlying member method code with example usage: obj.test_conversion_bad_inputs() without return types