code: def test_map_shrinks_code_storage_if_possible(self):
      arr = LabelArray(
          # Drop the last value so we fit in a uint16 with None as a missing
          # value.
          self.create_categories(16, plus_one=False)[:-1],
          missing_value=None,
      )
  
      self.assertEqual(arr.itemsize, 2)
  
      def either_A_or_B(s):
          return ("A", "B")[sum(ord(c) for c in s) % 2]
  
      result = arr.map(either_A_or_B)
  
      self.assertEqual(set(result.categories), {"A", "B", None})
      self.assertEqual(result.itemsize, 1)
  
      assert_equal(
          np.vectorize(either_A_or_B)(arr.as_string_array()),
          result.as_string_array(),
      )
  
imports: from itertools import product
  from operator import eq, ne
  import warnings
  import numpy
  from toolz import take
  from zipline.lib.labelarray import LabelArray
  from zipline.testing import check_arrays, parameter_space, ZiplineTestCase
  from zipline.testing.predicates import assert_equal
  from zipline.utils.compat import unicode
label_desc: Use image node_id 19 for calling the LabelArrayTestCase obj's underlying member method code with example usage: obj.test_map_shrinks_code_storage_if_possible() and returns: str,  str