code: def test_map_requires_f_to_return_a_string_or_none(self, f):
      la = LabelArray(self.strs, missing_value=None)
  
      with self.assertRaises(TypeError):
          la.map(f)
  
imports: from itertools import product
  from operator import eq, ne
  import warnings
  import numpy
  from toolz import take
  from catalyst.lib.labelarray import LabelArray
  from catalyst.testing import check_arrays, parameter_space, CatalystTestCase
  from catalyst.testing.predicates import assert_equal
  from catalyst.utils.compat import unicode
label_desc: Use image node_id 6 for calling the LabelArrayTestCase obj's underlying member method code with example usage: obj.test_map_requires_f_to_return_a_string_or_none(f) without return types