code: def test_get_conn_value(self, ssm_value):
      param = {
          "Name": "/airflow/connections/test_postgres",
          "Type": "String",
          "Value": ssm_value,
      }
  
      ssm_backend = SystemsManagerParameterStoreBackend()
      ssm_backend.client.put_parameter(**param)
  
      returned_conn_value = ssm_backend.get_conn_value(
          conn_id="test_postgres"
      )
      assert ssm_value == returned_conn_value
  
      test_conn = ssm_backend.get_connection(conn_id="test_postgres")
      assert test_conn.conn_id == "test_postgres"
      assert test_conn.conn_type == "postgres"
      assert test_conn.login == "my-login"
      assert test_conn.password == "my-pass"
      assert test_conn.host == "my-host"
      assert test_conn.port == 5432
      assert test_conn.schema == "my-schema"
      assert test_conn.extra_dejson == {
          "param1": "val1",
          "param2": "val2",
      }
  
imports: from __future__ import annotations
  import json
  from unittest import mock
  import pytest
  from moto import mock_ssm
  from airflow.configuration import initialize_secrets_backends
  from airflow.providers.amazon.aws.secrets.systems_manager import SystemsManagerParameterStoreBackend
  from tests.test_utils.config import conf_vars
label_desc: Use image node_id 2 for calling the TestSsmSecrets obj's underlying member method code with example usage: obj.test_get_conn_value(ssm_value) without return types