code: def test_create_memory_state_backend(self):
      self.assertIsNotNone(
          MemoryStateBackend("file://var/checkpoints/")
      )
  
      self.assertIsNotNone(
          MemoryStateBackend(
              "file://var/checkpoints/", "file://var/savepoints/"
          )
      )
  
      self.assertIsNotNone(
          MemoryStateBackend(
              "file://var/checkpoints/",
              "file://var/savepoints/",
              10000000,
          )
      )
  
      self.assertIsNotNone(
          MemoryStateBackend(
              "file://var/checkpoints/",
              "file://var/savepoints/",
              10000000,
              True,
          )
      )
  
      self.assertIsNotNone(
          MemoryStateBackend(
              "file://var/checkpoints/",
              "file://var/savepoints/",
              10000000,
              False,
          )
      )
  
imports: from pyflink.datastream.state_backend import _from_j_state_backend, CustomStateBackend, MemoryStateBackend, FsStateBackend, RocksDBStateBackend, PredefinedOptions, EmbeddedRocksDBStateBackend
  from pyflink.java_gateway import get_gateway
  from pyflink.pyflink_gateway_server import on_windows
  from pyflink.testing.test_case_utils import PyFlinkTestCase
  from pyflink.util.java_utils import load_java_class
label_desc: Use image node_id 2 for calling the MemoryStateBackendTests obj's underlying member method code with example usage: obj.test_create_memory_state_backend() without return types