docstr: Test that element_of raises a useful error if we attempt to pass it an
  array of choices that include the classifier's missing_value.
code: def test_element_of_rejects_missing_value(self):
      """
      Test that element_of raises a useful error if we attempt to pass it an
      array of choices that include the classifier's missing_value.
      """
      missing = "not in the array"
  
      class C(Classifier):
          dtype = categorical_dtype
          missing_value = missing
          inputs = ()
          window_length = 0
  
      c = C()
  
      for bad_elems in ([missing], [missing, "random other value"]):
          with self.assertRaises(ValueError) as e:
              c.element_of(bad_elems)
          errmsg = str(e.exception)
          expected = (
              "Found self.missing_value ('not in the array') in choices"
              " supplied to C.element_of().\n"
              "Missing values have NaN semantics, so the requested"
              " comparison would always produce False.\n"
              "Use the isnull() method to check for missing values.\n"
              "Received choices were {}.".format(bad_elems)
          )
          self.assertEqual(errmsg, expected)
  
imports: from functools import reduce
  import operator
  import numpy
  import pandas
  from zipline.lib.labelarray import LabelArray
  from zipline.pipeline import Classifier
  from zipline.pipeline.data.testing import TestingDataSet
  from zipline.pipeline.expression import methods_to_ops
  from zipline.testing import parameter_space
  from zipline.testing.fixtures import ZiplineTestCase
  from zipline.testing.predicates import assert_equal
  from zipline.utils.numpy_utils import categorical_dtype, int64_dtype
  from .base import BaseUSEquityPipelineTestCase
label_desc: Use image node_id 11 for calling the ClassifierTestCase obj's underlying member method code with example usage: obj.test_element_of_rejects_missing_value() without return types