class_docstr: ... purely for test coverage
code: def setup(self):
      self._driver = construct_persistence_driver({"driver": "null"})
      self._driver.set("this", "that")
      self._driver.set("those", {"theys": "thens"})
  
imports: from nose.tools import assert_equal, assert_raises, assert_true
  from streamalert.shared.lookup_tables.drivers import EphemeralDriver, NullDriver
  from streamalert.shared.lookup_tables.drivers_factory import construct_persistence_driver
  from streamalert.shared.lookup_tables.errors import LookupTablesConfigurationError
label_desc: Use image node_id 2 for calling the TestNullDriver obj's underlying member method code with example usage: obj.setup() without return types