code: def test_keys(self):
      d = self._empty_mapping()
      self.assertEqual(list(d.keys()), [])
      d = self.reference
      self.assertIn(list(self.inmapping.keys())[0], d.keys())
      self.assertNotIn(list(self.other.keys())[0], d.keys())
      self.assertRaises(TypeError, d.keys, None)
  
imports: import unittest
  import collections
  from test.support import Py_C_RECURSION_LIMIT
label_desc: Use image node_id 9 for calling the BasicTestMappingProtocol obj's underlying member method code with example usage: obj.test_keys() without return types